[youtube] decrypt signature when downloading dash manifest
Merge branch 'youtube-dash' of github.com:m0vie/youtube-dl
[youtube] Simplify the decryption process for the manifest urls and add a test (closes #2422)
[generic] Fix on python 2.6

`ParseError` is not available, it raises `xml.parsers.expat.ExpatError`.
The webpage needs to be encoded.
release 2014.02.21.1