Replace vendored auto_complete with gem auto_complete

And remove configuration that enabled auto_complete,
thus removing the warning.
Add rubocop TODO config file
Merge pull request #1446 from ferrous26/rubocop2

Add rubocop TODO config file
Merge pull request #1433 from ferrous26/vendor-be-gone

Replace vendored auto_complete with gem auto_complete. Closes #1324. Closes #670.