Scores

Several new scores implemented
Expanded testing including dask testing
Created pandas API for simple scores

This version of scores contains:
- Concrete implementation of a foundation set of scores
- 100% coverage unit testing
- Readthedocs website with all documentation
- Jupyter notebook tutorials for all scores
- PyPI installable

There are still required changes expected before this package is recommended for use beyond exploration of the scores.

Added MAE
Added MSE
Added CRPS

First version
Matching github documentation