Bugfix to getTemplate(), $http instead of $.ajax()

For some, reason if an external template (row/cell or header I would guess) is fetched with $.ajax(), and it receives a 304 (not modified) response, a "$digest is already running" error will occur while it is trying to add it to $templateCache.

Moving over to $http to do the get request seems to have fixed it. Was there a reason for the jquery/jquery-ish method?

I'd like to add a test for this, if possible, but it has been randomly breaking my app as 304s occasionally happen so I thought I would submit the pull request for now.