Potential memory leak for decoded frames in python

[David Yao]

Frameserver quickly fills up RAM when working with movie data, so I dug around and found this. Looks like buffer is never freed at https://github.com/scanner-research/hwang/blob/master/hwang/hwang_python.cpp#L88

pybind/pybind11#279 seems to suggest that pybind11 copies those bytes in buffer anyways.

This may be related to #2

[Will Crichton]

Fixed in 39d42cc