RemovedInDjango18Warning: get_query_set -> get_queryset

RemovedInDjango18Warning: commit_on_success is deprecated in favor of atomic.

accomodate older version of django

upgrade django to 1.7 from prerelease in travis

before_script migrate for dj 1.7 in travis

fix atomic for older version

remove unnecessary line from travis

revert to commit_on_success