add command that checks the state of each url belonging to a Video
fix a couple of errors with log and with missing url to check
Fix truncation of related urls urls

Previously the urls would get truncated, but there was no indicator they
were truncated. This adds an indicator.
Refactor checklinks command

* Create model to track Video URL statuses, add migrations and tests.
* Pull some of the checklinks.py functions into the new models
Sync up travis with tox config

Queue up the headesk bashing! I'm off to battle Travis again!