Email templates when user was added to group
New landing page when you have 0 projects
Fix bug with rendering changing images in commits

When viewing the diff for a changed image file, two bugs occur:

- Both the 'before' and 'after' images link to the 'after' commit
- Visiting the link for either image will cause a error

The first is caused by both image links referencing '@commit.id' rather
than '@commit.parent_id'.  The second is caused by the use of
'project_tree_path' which is used for creating links to directories in
the git file tree. 'project_blob_path' which links to files should be
used instead.
Rescue an error if group doesn't exist
Merge branch 'feature/new_landing' of /home/git/repositories/gitlab/gitlabhq
Merge pull request #5048 from Nullreff/image-diff

Fix bug with rendering changing images in commits
Add UsersGroup observer

Trigger notification service when new user-group relation was created
Enable UsersGroup observer, Add group_member methods to NotificationService
Fix typo in installation.md

SSH is pronounced as /es es aged/, so we need "an" instead of "a".
Compare page improved

* Show new merge request button from compare page
* Show message if user selected same branches
* Show message if compared branches are the same
* Prepend inputs with from/to labels
Right branches for mr link at Compare view
Merge branch 'argument_error_in_gitlab_check' of /home/git/repositories/gitlab/gitlabhq
Compare link for branches
Merge branch 'feature/email_when_added_to_group' of /home/git/repositories/gitlab/gitlabhq
Add default values to compare page link
Notice about moving projects.
Typo fix.
Replace remote url on selection.
Merge branch 'user-get-notified-on-move' of /home/git/repositories/gitlab/gitlabhq
Test.