WattTime Model improvements

[gnanakeethan]

Types of changes

• Enhancement (project structure, spelling, grammar, formatting)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

A description of the changes proposed in the Pull Request

Adding documentation

[jawache]

@gnanakeethan logic seems good but the documentation and code clarity/structure still needs a lot of attention.

[jawache]

If we start nesting data in observations I'm worried it's going to get very messy. In the issue I asked to use just lat,lon, if it's not clear I meant to use it as a string, I believe the WattTime API also just expects it as a string also. Let's stick to that approach and keep to a flat structure for observations for now. If we choose to nest it should be for good reasons and after a lot of thinking to make sure it won't cause more complexity problems downstream.

[gnanakeethan]

Agreed. I will flatten out. I did not go for single string because there are different ways people write latitude and longitude.

In the graph way, you give longitude first and then the latitude. It makes some unnecessary confusion to be taken in same input.

[jawache]

lgtm