Python 3.7 pip package

[justin1121]

We currently don't have a pip package for python 3.7 on linux. There seems to be an issue with the custom op docker container not allowing python 3.7 to work. We need to use this docker container to build custom operations so that the pip packages have the highest chance of working on all platforms.

See issue here: tensorflow/custom-op#25

[justin1121]

Should be able to build this now with manylinux2010 compatible build container tensorflow/custom-op#25