[mtv] Fix title for gametrailers (Fixes #2188)

We now prefer the title including the category, because that title is what is presented at the actual sites.
[mtv] Use unicode_literals
[gametrailers] Use unicode_literals

Conflicts:
	youtube_dl/extractor/gametrailers.py
Merge branch 'master' of github.com:rg3/youtube-dl

Conflicts:
	youtube_dl/extractor/mtv.py