Merge branch 'github-no-omniauth' into 'master'

Don't require omniauth to enable github importer

I noticed the github importer is only enabled when omniauth authentication is also enabled. That isn't actually necessary -- just the oauth keys from GitHub are required to be configured.

The fix for this is very simple.

See merge request !316

app/helpers/projects_helper.rb

@@ -263,7 +263,7 @@ module ProjectsHelper
   end
 
   def github_import_enabled?
-    Gitlab.config.omniauth.enabled && enabled_oauth_providers.include?(:github)
+    enabled_oauth_providers.include?(:github)
   end
 end