Merge pull request #9 from Yepoleb/httpapi

Add support for some http api calls
Support for paged feeds (RFC 5005) with podcastparser 0.3.0

http://podlove.org/paged-feeds/
http://tools.ietf.org/html/rfc5005
Remove leftover debug output
Fallback to audio/video link if no enclosures are found
Add support for Podlove Simple Chapters

Requires podcastparser 0.4.0.
gpodder.download: Send initial progress report immediately
Various small PEP-8 fixes
Return 100% progress if episode is downloaded