create a concern to handle with some omniauth methods
remove some unused code :)
fix broken spec on PaymentEngines
remove contributed_by and contributed_projects from project and user and added the contributed_projects via has_many ;)
Merge branch 'master' into added_some_concerns
Merge pull request #754 from devton/added_some_concerns

Added some concerns and refacts <3
added user_notifier gem and its configuration
adding user notification using the UserNotifier gem and moving some templates to be used by the gem
removed unused User#notify method
moved user_deactivate notification template
moved credits warning templates and fixed user_deactivate subject template
fixed observer spec
fixed user notifications
created contribution_notifications table
migrated notify calls to user_notifier gem, still need to migrate templates
moved payment_slip templates
moved refund_completed and refund_completed_slip templates
moved refund_request templates
moved refunded_and_canceled templates
moved request_refund and request_refund_slip templates