Pynucos

Fixed a bug with `GetUnitNames()` and capitalization.

Added code to get valid unit names for a given unit_type

Just a removal of extraneous debug prints.

And a couple new unit aliases

This release chances the standard package import to `nucos`:


import nucos

nucos.convert("g", "kg", 1000)

NOTE: the old `unit_conversion` import still works, but will give a `DeprecationWarning`

This version adds the Mass Fraction nanograms per gram unit.

The unit tests now require Python 3.7 and above.

The rest of the code will probably still work on Python2 -- but that won't be tested or maintained anymore.

Other changes:

- Conversion value for Specific Gravity at 15C has been changed in the fourth digit to match the standard used by the Petroleum Industry.

- Tests have been cleaned up to use pure pytest - no more unittest tests.