Automatically link commit ranges to compare page.

Closes #2103

Implemented as proposed in the last paragraph of the issue:

> We could do something similar to Ruby, where `1..5` means `1,2,3,4,5` and `1...5` means `1,2,3,4`: `..` means inclusive, `...` means exclusive. In our case, `sha1...sha4` would mean `sha2,sha3,sha4` (exclusive with regards to `sha1`) and `sha1..sha4` would mean `sha1^...sha4`, i.e. `sha1,sha2,sha3,sha4` (inclusive to `sha1`).

- `sha1...sha4` now links to `compare/sha1...sha4`
- `sha1..sha4` now links to `compare/sha1^...sha4`.

See merge request !1649

GitLab UI development kit and UI guide help section

Page with UI elements get generated from current css so you can immediately check how your css changes affects common ui elements. Because it requires GitLab runnning I cannot put it to documentation so I just put link to localhost from development section

cc @developers @sabba @sytse

See merge request !1653

Mobile improvements for user page

* hide calendar on small screens
* hide sidebar and show button to toggle it

Fixes #2101

See merge request !1652

Reduce amount of custom css and increase usage of default bootstrap

* Copy variables template file for configuring bootstrap variables
* Move layout and bootstrap to `base/` directory and explicitly set import order
* Apply some styles from flatly theme
* Replace bs-callout with alert
* Refactor gitlab css state colors
* Cleanup css variables
* Remove custom css for panels and navs

See merge request !1651

Fix editor in IE producing errors #1096

IE seems to handle form submission oddly. It gets fired twice - once from javascript and once from the form click, producing 2 identical requests and causing #1096.

Similar issues: http://stackoverflow.com/questions/14373800

Returning false from the click event seems to fix it and shouldn't cause any side-effects.

See merge request !366

use constant-time string compare for internal api authentication

Send notifications and leave system comments when bulk updating issues.

Resolves https://dev.gitlab.org/gitlab/gitlabhq/issues/1885.

See merge request !1646

Condense commits already in target branch when updating merge request source branch.

Resolves https://dev.gitlab.org/gitlab/gitlabhq/issues/2043.

![Screen_Shot_2015-03-06_at_17.17.13](https://dev.gitlab.org/gitlab/gitlabhq/uploads/8d03540b7b7294ce07005e6f3db6ed3d/Screen_Shot_2015-03-06_at_17.17.13.png)

(Not shown in screenshot, but works fine with rebases as well)

See merge request !1648

 Add tag push notifications to HipChat and Slack messages and normalize output of messages to be consistent

Add tag_push event notification to HipChat and Slack services.

For each service, normalize message output to use:
- User name instead of username
- Include first line of title in message description
- Link to "Issue #X" instead of "#X"

See merge request !370

Ruby str_equal uses memcmp internally to compare String.
Memcmp is vunerable to timing attacks because it returns early
on mismatch (on most x32 platforms memcmp uses a bytewise comparision).
Devise.secure_compare implements a constant time comparision instead.

Normalize output to use:
- User name instead of username
- Include first line of title in message description
- Link to "Issue #X" instead of "#X"

Use bootstrap buttons with custom colors instead of own css

Reduce amount of custom css will make UI development easier

See merge request !1641

Add notes notifications to services

This merge request builds on top of a few other merge requests:

* https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/237
* https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/350

The purpose of this merge request is to add service notification support when a user comments on one of the following:

* commits
* issues
* merge requests
* code snippets

Currently HipChat and Slack are only supported. The admin can select which events to toggle on or off.

## Questions

All note events are bundled under the `note` event type. Is this okay, or does it make more sense to have individual events and/or change the `object_type` attribute in the hook data?

Also, does it look better to link the entire `merge request #X` as opposed to just `#X`? I like the former.

## Before

![Screen Shot 2015-03-01 at 3.05.56 PM](https://gitlab.com/uploads/stanhu/gitlab-ce/8ae828e652/Screen_Shot_2015-03-01_at_3.05.56_PM.png)

## After

![Screen Shot 2015-03-06 at 6.24.40 AM](https://gitlab.com/uploads/gitlab-org/gitlab-ce/7b866ae02b/Screen_Shot_2015-03-06_at_6.24.40_AM.png)

### Slack

![Screen Shot 2015-03-01 at 2.59.00 PM](https://gitlab.com/uploads/stanhu/gitlab-ce/0147c2dc38/Screen_Shot_2015-03-01_at_2.59.00_PM.png)

### HipChat

![Screen Shot 2015-03-01 at 2.59.19 PM](https://gitlab.com/uploads/stanhu/gitlab-ce/14e78fc61c/Screen_Shot_2015-03-01_at_2.59.19_PM.png)

See merge request !358

Supports four different event types all bundled under the "note" event type:

- comments on a commit
- comments on an issue
- comments on a merge request
- comments on a code snippet