Correct link and mention EE in readme for MySQL packages
Update the backports gem to 3.6.3

This fixes 'Bad file descriptor' errors during the build on Centos 6.
Merge branch 'update_backports' into 'master'

Update the backports gem to 3.6.3

This fixes 'Bad file descriptor' errors during the build on Centos 6.

See merge request !232
Added .idea to .gitignore for JetBrains based IDEs
Do not use single quotes when inserting external_url.
Merge branch 'master' of dev.gitlab.org:gitlab/omnibus-gitlab