Upgrade to support Python 3

Python 2 end of life is Jan. 1, 2020. This program is now re-written to do away with Python 2 and runs on Python 3 instead.

ThxsPy first release

This is the first release of ThxsPy - a python program to help you convert mass spectrometer uranium and thorium isotope count data to isotopic activity. In this version of the program, the file reading function has been completely revamped to use the powerful pandas library. This allows the program to be more flexible with the input files.