Merge pull request #19 from Xeoncross/multiple-http-backend

Use cURL follow-redirects instead of manual looping forever.
Remove code duplication and add unit tests
Add callback functions for curl to read body and headers + abort on large body
Remove duplicate code
Abort on large body (Stream backend)
Remove PHP notice
Add iframe allowed resources
Update readme
Add HTML5 video tag in Filter class
Convert to string author field for Atom feed
Item id is a hash of the item url and the feed url now
Change id generation
Add HTML5 audio tag
Add new URI scheme
Typo fix
Allow people to override blacklist/whitelist for content filtering
Update readme
Fix #21: ignore bad attribute values
Remove old libxml2 workaround and ignore XML errors silently
Improve filter (remove empty tags…)