cmake is required during the installation of the rugged gem

Update changelog

Fixes #146

See merge request !149

Fix spelling error in merge request performance issue warning.

Conflicts:
	doc/workflow/README.md

Fix merge request API after #7526

Fix labels preview color when edit

This is related to #515. Parentheses are missing in coffeescript. For this reason, the color preview is not updated when loading the labels edit page.

See merge request !173

Label doc

Fixes #1487

See merge request !1028

Conflicts:
	VERSION

Update omniauth-google-oauth2 gem

#### What does this MR do?

This PR updates google omniauth gem.

#### Why was this MR needed?

This is needed, because google deprecates some API on Sept, 1st.

All tests pass, but I still have to ~~test and update documentation in https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/integration/google.md~~

**Contacts API" and "Google+ API need to be enabled**

This need to be stated in the update guide (7.1 to 7.2), as well as (6.0 to 7.2)

This fixes #512

See merge request !171

API: Labels validation in issues API

Conflicts:
	VERSION

Skipping rc3 because somebody (me) created a tag but did not bump the
version to rc3.

Fix project description on explore page, fixes #7458

use default white-space for sidebar buttons, fixes #7549

Show shared groups

Fixes #134

See merge request !148

Email

Fixes #126

See merge request !150

Fix color toggle for labels in edit view

Conflicts:
	VERSION