Also parse the `adaptive_fmts` key

In order to be ready for either
  1. YouTube support of HTTP Live Streaming  (HLS)
  2. iOS support of Dynamic Adaptive Streaming over HTTP (MPEG-DASH)

Incidentally it also fixes #19 since YouTube removed the `sig` key and directly includes the `signature` parameter in the video URL.
Version 1.1.2
Update CHANGELOG for version 1.1.2
Merge branch 'hotfix/1.1.2'