Checking if track length is defined before displaying it.
Fixed url processor for YouTube links.
Added exception catching into url processors.
Fixed CB-32.
Fixed incorrect review creation date on release group page.
Fixed incorrect decoding of wiki urls.
Simplified track_length() function. (thanks ruaok)
Merge branch 'cb-30' into stage1
Merge branch 'cb-32' into stage1
Merge branch 'cb-35' into stage1

Conflicts:
	client/critiquebrainz/apis/musicbrainz/relationships/artist.py
	client/critiquebrainz/apis/musicbrainz/relationships/release_group.py