Null dereference check.
Use an iPad user agent to grab the HD version of videos.
Merge remote-tracking branch 'larcus94/master'

Conflicts:
	LBYouTubeView/LBYouTubeExtractor.m
Merge pull request #60 from ksuther/master

Null dereference check
Rename user agent constants
Update Readme
Merge commit 'cc50dee15701b672b11bfdd1990135f0a34205c4'

* commit 'cc50dee15701b672b11bfdd1990135f0a34205c4':
  Update Readme
  Rename user agent constants
  Use an iPad user agent to grab the HD version of videos.
  Null dereference check.

Conflicts:
	LBYouTubeView/LBYouTubeExtractor.m