Updated Slack documentation

Fixes #2234

Updated the Slack documentation to include the new fields located in the service's settings.

/cc @karen

See merge request !1788

Recover from URI::Error

`URI::Error` is the base class for all URI errors.

Fixes #2257 and #2260

See merge request !1789

add 7.9-7.10 upgrade doc

See merge request !560

Fix user API tests succeeding for the wrong reason

Update gitlab-grack to 2.0.2.

Updating to grack version 2.0.2 to fix an issue with smart http clients.

See merge request !559

Remove html-pipeline-gitlab

Ports the custom emoji filter to the app itself.

See merge request !1781

Fix tab behavior on MergeRequests#new

Missed this one in 269aee79

Prior to this fix, clicking the Commits or Changes tab when creating a new MR would reload the page instead of display the tab contents.

See merge request !556

Make issue preview look like the result

do not send empty message to hipchat

The requests were missing multiple required attributes, while testing for single attribute missing.
Added test for checking username as required attribute.

Fixes #2257
Fixes #2260

Didn't like relying so much on Regex matches

Removes emoji-centric tests from GFM specs 💥

Convert GFM reference handling to html-pipeline filters

- `Gitlab::Markdown` is now much cleaner
- Better separation of concerns
- Cleaner, less brittle, more maintainable specs for each reference type.
- Label references actually work!

See merge request !1753

add environment variable force to the documentation

Remove entry that was shipped in v7.9.1

See merge request !532

7.10 requires gitlab-shell 2.6.2.

Fixes #1467.

See merge request !552

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

Conflicts:
	app/controllers/import/google_code_controller.rb

Fix some issues with Google Code importer

Thanks, @mrtux, for reporting all of these.

See merge request !551

Update gitlab-grack to 2.0.1 to get unicorn to stop creating zombies.

Addresses #1461 and private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2253.

This regression was introduced between 7.9 and the 7.10 rcs, so no changelog item for 7.10 proper.

cc @JobV @jacobvosmaer

See merge request !546

upgrade hipchat

Fix "Cannot move project" error message from popping up after a successful transfer

The JavaScript click handlers were never being removed, leading to duplicate requests when attempting to transfer a project to another namespace. The first transfer would succeed but the subsequent ones would fail, leading to the error message saying, "Cannot move project".

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/0c9f61294291514e0c2a48c204b6a1aa/image.png)

I attempted to write a unit test for this, but it was taking me too long to get it right.

Closes #1448 and #1128

See merge request !548