lwtnn/lwtnn: Version 2.10

This release adds a few minor things to python code. Nothing changes any C++ code but there are some fixes and extensions in the python:

• Use a "swish" activation function which is more similar to that in keras-contrib (thanks @aghoshpub)
• Some sequential models from more recent versions of keras were breaking keras2json.py, fixed this
• Added a slightly more robust check for consistency between the CMake version and the tag in git