Changed post edit subtitles permissions check (#483)
Fix post edit permissions for language manager (#483)

Refactored the unittests a bit so that we can test this stuff more
easily.
Fixed can_add_version() permission

Made it send the language code to can_post_edit_subtitles()
updated the edit and rollback test cases for new pemission behavior in gh-483
Merge pull request #878 from pculture/gh-483

Gh 483