Adds spiceinit'd cube driver (#73)

* Removed abstract base class from drivers

* First pass at spiced cube driver

* Actually added cube driver

* Added numba dependency

* Made cube driver less stateful

* Added messenger spiceinit'd driver

* Finished cube driver

* Added cube driver test

* Cleaned up and renamed cube driver

* Renamed ISIS SPICE driver file

* Updated ISIS SPICE test with new names

* Renamed ISIS SPICE test file

* Reverted changes in mdis driver post merge

* Partially fixed ISIS SPICE test

* ISIS spiceinit driver now works and is tested

* Added exception handling and fixed start time logic

* Added numpy style docs

* more clean up

* deleted test cube io notebook

* added more docs