TypeError: seek() got an unexpected keyword argument 'mode'

Created by: pi-bjl

Hello,

I see 0.4.0 has just been released.

Looking at https://github.com/mikeboers/PyAV/compare/v0.3.3...v0.4.0 , It looks like the Stream.seek keyword argument 'mode' has been renamed to 'whence'?

Also, I don't know if this intentional, but in av/data/stream.pyx it has class DataStream(Stream) with seek method which still has a 'mode' argument.

I guess this should be included in #297 (closed), or possibly changed back to 'mode' to keep backwards compatibility.

Thanks!