Renamed the main class to opengraph to conform to documentation
Avoid throwing a KeyError if the document does not contain any RDFa tags
Fixed "import" statement in documentation
Refactored to use pyRdfa directly (no longer via rdfadict which is just a trivial wrapper to pyRdfa). This makes us more flexible since we now control the whole interface to pyRdfa
Added workaround for YouTube invalid OpenGraph tags
Merge pull request #1 from ahtih/master

Various fixes