Move OmniAuth configuration details into a non-revision controlled file.

Ensure LDAP provided email is always compared case-insensitively.

Useful for Sqlite or Postgres installations.

Changed for mysql2 adapter

Texting issues fix

Fix installation instructions for running gitlab_status

When running `rake gitlab_status` to check if it's safe to continue on installation in step 4, you need to use `RAILS_ENV=production` or else you will receive an error about "permission denied for user root@localhost..."

See https://github.com/gitlabhq/gitlabhq/issues/572