Log Message:
py-lz4: updated to 0.18.1

0.18.1:
This is a minor bugfix release which fixes two small bugs which would result in \ 
source references not being released on error conditions in lz4.frame.compress.

0.18.0:
This release changes the strategy for allocating memory to not use undocumented \ 
and potentially fragile Python internals (Py_SIZE). This may have a small \ 
performance impact, but brings stronger guarantees for future stability.