Update 6.9-to-7.0.md

fix gitlab.yml example diff command
fix high cpu usage issue that occured in Firefox

fixes issue related with #342 (Merge Request view causes 100% CPU in firefox)
Gitlab::Git::Compare in Satellite::CompareAction
Integrate lessons from the latest release.
Based on http://www.reddit.com/r/linux/comments/2bffgt/gitlab_71_released/cj59wvz reword this requirement, thankstictatonifonical.
Note exim problems.
Merge branch 'word-requirement-a-bit-more-realistic' into 'master'

Word requirement a bit more realistic

See commit message

See merge request !155
Add warning about backing up the config.
Merge branch 'backup-settings-warning' into 'master'

Backup settings warning

Fixes #1457

See merge request !992
Explain project services.
Merge branch 'project-services-explained' into 'master'

Project services explained

See merge request !993
Merge branch 'exim-problems' into 'master'

Exim problems

After merge report back to https://github.com/gitlabhq/gitlabhq/issues/4866

See merge request !990
Add a tip on how to test regular expressions
Merge branch 'master' of gitlab.com:gitlab-org/gitlab-ce
Most starred projects page for Explore area

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Moved some behaviour to one place

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>
Tests for trending/starred pages

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'most-starred' into 'master'

Most starred projects page

Fixes #1461

See merge request !996
Merge pull request #7319 from jvanbaarsen/small-eventcache-refactoring

Moved some behaviour to one place
Add missing semicolon in application.scss