Added Ajax Error Handling

Added an error message when an ajax error occurs. This can be
overridden through the select2 option “formatAjaxError”.
gitignore
Revert "gitignore"

This reverts commit d19bb1c32cbc1191c19b01f0db34f8d7f0601fc8.
Merge pull request #2491 from Ermish/master

Added Ajax Error Handling