e.g.: the sidekiq in my Debian box is v2.11.1

It returns "yes" if required version is "1.7.10" and current version is "1.6.10",
because the patch version of current version equals to that of required version.

Checking is "yes" only if git version equals "1.7.10" exactly.

Checking the redis version will warn users that
are using an old version to update. Included
reference to the troubleshooting guide.

Checking the redis version will warn users that
are using an old version to update. Included
reference to the troubleshooting guide.

Fixing issue #2970

Running the recommendation would give out:
GNU find: paths must precede expression

Fixes #2608

The tasks gitlab:env:info mixes user and group, and presume as a group 'git'.
However, gitolite group name can be anything.

That patch add the git group name in the config,
and check gitolite.ssh_user group against git.group
(which defaults to 'git', as before this patch, if undefined).

M config/gitlab.yml.example:
  Add 'group' in 'git' section
  Mention default value for the two extra settings
M lib/tasks/gitlab/check.rake:
  Check that gitolite.ssh_user *group* is the one defined in git.group.
  Make sure to default to 'git' as the expected group
    if said group is undefined in the config.
  Note: uses a more complete regexp for the group detection
        (the group can start, end or be in the middle or the list of groups
         of gitolite.ssh_user)
M: config/initializers/1_settings.rb:
  Add default values for gitolite.group and gitlab.user

Fixes #2475

Fixes #2496