Change percent_complete rescue value from 100 to 0

The percent_complete method returns a value of 100 when a
ZeroDivisionError occurs. That seems like a very strange default for an
error case, and results in a bug when a milestone has no corresponding
issues (new, empty milestones show 100% completion). This commit changes
the rescue value to 0, and subsequently fixes #1656, which reported this
problem.

See merge request !714

The percent_complete method returns a value of 100 when a
ZeroDivisionError occurs. That seems like a very strange default for an
error case, and results in a bug when a milestone has no corresponding
issues (new, empty milestones show 100% completion). This commit changes
the rescue value to 0, and subsequently fixes #1656, which reported this
problem.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Validate wiki page creation

Fix Zen Mode not closing with ESC key

### What does this MR do?

This MR fixes the ESC key not leaving Zen Mode (fullscreen).

### Why was this MR needed?

This has been broken since GitLab v7.8. The `change` event for `zen-toggle-comment` was never fired. See:

http://stackoverflow.com/questions/19505011/checkbox-checked-with-prop-does-not-fire-events-attached-to-change?answertab=votes#tab-top

### What are the relevant issue numbers?

* Closes #1025
* Closes https://github.com/gitlabhq/gitlabhq/issues/9018

See merge request !710

**What does this do?**
It adds validation to the creation of a wiki page, that way the user gets real
feedback instead of just a 404 page if the name of the wiki page was invalid

**Why is this needed?**
There are a lot of characters that are not allowed in the creation of a wiki
page, there is even a small text that is saying: Please don't use spaces.
Although we have that text there, we don't actually validate on this. This
commit adds validation on the title and gives the user actual feedback.

**What issues does this fix?**
Fixes http://github.com/gitlabhq/gitlabhq/issues/5357
Fixes https://github.com/gitlabhq/gitlabhq/issues/8565
Fixes https://github.com/gitlabhq/gitlabhq/issues/3913
Fixes https://github.com/gitlabhq/gitlabhq/issues/8166Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Use .md as extention for wiki pages

**What does this do?**
It makes sure that when you create a wiki page via the web interface, the
extention is .md instead of .markdown

**Why is this needed?**
When you're using Gollum locally, it will create pages with the .md extention.
Also .md is the best known extention for markdown. This fix will make sure that
if you're using gollum or the webinterface, the extention will be the same.

**What issues does this fix?**
Fixes https://github.com/gitlabhq/gitlabhq/issues/5204Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Add link_to_label helper

The primary purpose of this change was to make the actual labels on `Labels#index` clickable.

See merge request !690

Update ffaker gem

Adds a version requirement which it didn't have before, at 2.0.0. This version has breaking API changes in that the namespace is now `FFaker` instead of `Faker`.

Prior, if a new developer checked out the repo, ran `bundle install` and then tried `rake dev:setup`, seeding would fail due to having the latest version of ffaker without the API changes in this MR.

Also updates `spring` version and the binstubs, just for kicks.

See merge request !686

Better handle label references that aren't actually references

Fixes #1690

See merge request !705

Fix Markdown preview not working in Edit Milestone page

### What does this MR do?

This MR removes the automatic Zen Mode URL update when a hash is present and makes Markdown preview work again in the Edit Milestone page. I think the intent was to make it possible to link to a full-screen edit with a URL (e.g. http://foo/bar/issues/1/edit#fullscreen), but I don't this has ever worked. Perhaps a future MR can support this.

### Why was this MR needed?

A JavaScript error would be seen in the Milestone Edit page:

```javascript
Uncaught error, unrecognized expression: $('.zennable input[type=checkbox]##md-preview-holder')
```

In the Milestone Edit page, apparently the use of the hash `#md-preview-holder` causes the Zen Mode JavaScript to attempt to parse the hash for the `fullscreen_` prefix and look up the checkbox based on a unknown ID.

### Are there points in the code the reviewer needs to double check?

If we want to keep this hash update, an alternative fix is to add an `if` check in the beginning of `checkboxFromLocationHash`:

```coffeescript
if (window.location.hash.indexOf('#' + ZenMode.fullscreen_prefix) == -1)
  return null
```

### What are the relevant issue numbers?

* Closes #1687
* Closes https://github.com/gitlabhq/gitlabhq/issues/9325

See merge request !711

Refactor permission checks with issues and merge requests project settings

Slight refinement for read/write permission checks for 04d44522 as discussed in !691. Currently it appears that there is [no role that only has read-only access to issues](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/permissions/permissions.md), but it could be possible.

/cc: @DouweM

See merge request !704

Remove Rack Attack monkey patches and bump to version 4.3.0

I finally got these monkey patches into Rack Attack v4.3.0, so GitLab no longer needs them. Hooray!

See: https://github.com/kickstarter/rack-attack/pull/128

See merge request !693

Added documentation styleguide

Hi. I added a documentation styleguide and linked it to https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides

See merge request !709

Added note about backups for gitlab.com

Added note about backups for Gitlab.com based on question on Twitter
https://twitter.com/MarcelloLins/status/598544357294272513

See merge request !1828

Closes #1687
Closes https://github.com/gitlabhq/gitlabhq/issues/9325

Closes #1025

Document expanded autolinking in doc/markdown/markdown.md

See merge request !706

Time zone text fix

Added small fix to /etc/gitlab/gitlab.rb

See merge request !1830

Fixes #1690

Disable "New Issue" and "New Merge Request" buttons when features are disabled in project settings

Closes #1676

See merge request !691

Closes #1676