Added support for EXT-X-ALLOW-CACHE

http://tools.ietf.org/html/draft-pantos-http-live-streaming-10#section-3.4.6
Only write EXT-X-ENDLIST if playlist type is VOD
Added support for EXT-X-PROGRAM-DATE-TIME

http://tools.ietf.org/html/draft-pantos-http-live-streaming-10#section-3.4.5
Missing comma fix for EXT-X-ALLOW-CACHE
Add date to the list of properties for Item
Fixed the VOD playlist type check
Added tests for EXT-X-ENDLIST
Merge pull request #2 from jhurliman/master

Adding support for live playlists, EXT-X-ALLOW-CACHE, and EXT-X-PROGRAM-DATE-TIME