Add documentation for `get_historical_data`, `get_city_station_options`, and `get_city_forecast` to the gh-pages documentation

[Milind220]

The methods page of the official API documentation explains every public method in Ozone and shows how it can be used.

Three new methods have been added, for which there is no complete documentation right now:

• get_historical_data
• get_city_station_options
• get_city_forecast

[Milind220]

Hold my beer, I got this

[Milind220]

I'm going to make these changes directly in the gh-pages branch. In methods section:

• [ ] get_historical_data
• [ ] get_city_station_options
• [ ] get_city_forecast

[Milind220]

I've been thinking about documentation for Ozone, and I think perhaps GitHub pages wasn't the best choice for this. It requires too much baby-sitting to update for each method. I'm going to look into some automatic documentation generators, that could use our method docstrings to generate documentation.