Add 'proposed tweet' for RC1

See merge request !835

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

Conflicts:
	Gemfile.lock

Fix duplicate 'Email has already been taken' message when creating a user

devise :validatable and validates uniqueness set on the user email field cause 2 validations to fire when creating a new user with an email address already in use, Issue 6123

@stanhu Thanks for your input on merge request 807, I'll close that one in favour of this as I have added tests

See merge request !817

Prefix 2FA issuer with the GitLab host (e.g., 'dev.gitlab.org')

https://dev.gitlab.org/gitlab/gitlabhq/issues/2373

See merge request !821

added info about migrating to gitlab.com

Added useful information. Because of tweet https://twitter.com/A_Makedonsky/status/610860840036749314

See merge request !1870

Bump rails to 4.1.11, jquery-rails to 3.1.3

rails 4.1.11 notes - http://weblog.rubyonrails.org/2015/6/16/Rails-3-2-22-4-1-11-and-4-2-2-have-been-released-and-more/

jquery-rails < 3.1.3 security advisory: https://groups.google.com/forum/#!topic/ruby-security-ann/XIZPbobuwaY

See merge request !830

Random Bootlint fixes

See merge request !822

Support commenting on a diff in side-by-side view

### What does this MR do?

This MR adds support for commenting on a diff in side-by-side (aka parallel) view. It also fixes a JavaScript bug (see !779) when the comment button is clicked on a line that already has a comment.

There is an existing bug where the comment count is not updated when a new comment is added. I'll send a MR for that later.

### Why was this MR needed?

Commenting only worked in "inline" mode. Often the side-by-side view is more conducive to writing comments.

### What are the relevant issue numbers?

Closes https://github.com/gitlabhq/gitlabhq/issues/9283

### Screenshot

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/3d0a3213fde38844a681a826da18139b/image.png)

See merge request !810

Closes https://github.com/gitlabhq/gitlabhq/issues/9283

If kerberos is enabled require it

Since 'group: :kerberos' got [included in the Gemfile ](https://gitlab.com/gitlab-org/gitlab-ce/commit/2391a43a7073b4e723e9ca1f7ff19b30f8e51452) Kerberos no longer got [loaded when the app started](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/application.rb#L6)

This caused `Devise::OmniAuth::StrategyNotFound` error once Kerberos is enabled, failing to start GitLab .

With this we hopefully do not need to remove group from the Gemfile.

See merge request !819

Fix layout issue in header title truncation.

@douwe Thanks for reviewing this fix for the issue mentioned in https://dev.gitlab.org/gitlab/gitlabhq/issues/2314#note_48539.

**BEFORE**

![before](https://dev.gitlab.org/gitlab/gitlabhq/uploads/4ffb35f77155a92c64cfe36c66987eb0/before.gif)

**AFTER**

![after](https://dev.gitlab.org/gitlab/gitlabhq/uploads/2bb2d0c4a93164f6d47e24cdcb9a106b/after.gif)

See merge request !1867

Fix UI issues in Applications form

@douwe Thanks for reviewing this small fix.

---

Before:

![application_form_before](https://dev.gitlab.org/gitlab/gitlabhq/uploads/11fbee17ad6a4c9456cd7d6cba5ae429/application_form_before.png)

---

After:

![application_form_after](https://dev.gitlab.org/gitlab/gitlabhq/uploads/0c64214ccda6c77095f468fcb8c748f3/application_form_after.png)

See merge request !1859

Fix hooks for web based events with external issue references

The creation of cross references for external issues (which would fail)
is now prevented. This fixes a 500 error and the execution of hooks when
creating a merge request or commenting on one.

Fixes #1650, GH-9333.

This regression might have been introduced by
8f8a8ab3. There is actually a TODO by
@rspeicher mentioning external issues which is lost (unhandled) in a
later commit.

This fix is related to !766 and !804 which fix a similar issue for hooks for
Git based events.

See merge request !794

Update release doc

See merge request !1865

Improve DB dump instructions

See merge request !1868

New syntax of .gitlab-ci.yml

See merge request !1862

Look for .gitlab-ci.yml only if checkout_sha is present

Fixes https://dev.gitlab.org/gitlab/gitlabhq/issues/2396

cc @vsizov

See merge request !818