Fixed updating internal note

[agnessa]

https://www.pivotaltracker.com/story/show/118548989

The bug would only manifest itself where a nomenclature_comment object existed before the nomenclature change. Where none existed, it would be created with the internal note correctly, but if it existed before, the changes to the text would not save on tc.save - it needed an extra nomenclature_comment.save

[coveralls]

Coverage increased (+0.01%) to 80.202% when pulling f80fb70 on fixed_updating_internal_note into c355451 on nomenclature_changes.