Rounder and sounder

This release brings a bit more sanity to the rounding behaviour of the conversions to lat/lon coordinates. If your input coordinates are in whole metres then the lat / lon output will be automatically rounded to 6 places, which is more than enough for +/- 1m accuracy. More detail in the docs.

Also there are some new scripts, improvements to others, and better test coverage and error handing.

Corrected Python2 / Python3 array issue

• Documentation at https://grid-banger.readthedocs.io/en/latest/index.html
• Moved all functions from mapping module into gridder
• Fixed issue with array.array methods for Python2 v Python3