Themisasi

Redo API to be oriented around path, site, time instead of specific filenames

python
import themisasi as ta
dat = ta.load'~/data/', 'gako','2011-01-01T06:32:10')

Use easy CDFlib instead of bulky SpacePy to read CDF

make time handling more robust and tested

* add pixel time series plot function
* functionalize more
* improve test coverage into fov.py
* generally lots more checks and test

* pep8, mypy, setup.cfg

pep8, mypy, pytest. Should be robust.