[REQUEST] Be Very Clear about Units

[PaulWAyers]

Is your feature request related to a problem? Please describe.

We need to be very clear about units. If I'm not mistaken, everything in GBasis is in atomic units. While we are specific about atomic coordinates being in a.u., we should be specific about point-sets passed in, basis functions, and the properties/integrals too, as it isn't entirely obvious.  

One could document the most important functions explicitly and put a note at the bottom of the main web page/Readme to cover cases where we don't explicitly indicate units.