[Feature] - Added signature, gdata, basic and size parameters to new()
These parameters can be used to restrict the data fetched on instantiation
of Pafy objects and can significantly reduce the time taken to create new
instances. Any missing data will be fetched when needed.
[Feature] - Javascript is released internally once functions are extracted
Smaller memory footprint for Pafy / Stream objects
[Bugfix] - release unneeded internal data, smaller pafy objects
[Update] - getbest and getbestaudio() return None if no streams available
[Update] - Pafy raises ValueError or IOError. RuntimeError removed
[Update] - len() has been removed. use .length property instead
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20 February 2014