Mgrs

* Fix up install requirements 34 (thanks jwilges )

* Alias and deprecate RTreeError 33

* MGRS now requires packaging library 31
* Fix wheel imports of shared libs

* UTF-8 encoding for all strings.
* Fix 29 implicit tuple on return of UTMToMGRS

* automated building of osx, linux and win64 wheels
* Migrate from TravisCI => GitHub Actions
* Warnings cleanup
* flake8 validation