Nygrid

Add documentation.

What's Changed
* Feature/docs by boyuan276 in https://github.com/boyuan276/NYgrid-python/pull/23
* Feature/docs by boyuan276 in https://github.com/boyuan276/NYgrid-python/pull/24


**Full Changelog**: https://github.com/boyuan276/NYgrid-python/compare/v0.1.1...v0.1.2

Release NYgrid-python package on PyPI.

This is a pre-release version v0.1.1-alpha. It contains code for running the NYGrid model for the base year 2018 with updated paramsters (2018NewParams), and also three policy scenarios for the future year 2030 (2030BaselineCase, 2030ContractCase, and 2030StateScenario).