python3 GIL locking solution

[excaliburtb]

Implemented use of the python GIL API to replace the less portable mutex solution.

[excaliburtb]

i titled it python3 but it still works with 2.7.18 as well

[coveralls]

coverage: 55.86% (-0.05%) from 55.906%
when pulling 499cb1f on excaliburtb:fix_python_gil_locking
into d4f92cc on nasa:master.

[hchen99]

Thanks for the fix. According to https://docs.python.org/3/c-api/init.html#non-python-created-threads, for non python created threads, using GIL is the way suggested.