Python Version-Agnostic Support

I have updated the project to be python version-agnostic, meaning that it should work with both python2 and python3. As a tool that is designed to function with the libraries and packages on the system it is run on in-place, it should not rely on a specific version of python and should strive to be as inclusive as possible. This release should drastically widen the potential use-cases for kernelpop.

Again, please let me know if you find any issues!