Improve documentation

[mfosterw]

While there is a lot of documentation within the code, there are still significant problems with the documentation available on the documentation page, particularly for model fields and classes inheriting from libraries.

• Fix APIDocs #22
• Add installation guide to contributing docs #23
• Fix up contributing guide #24
• Add better documentation for models
• Add docstrings to any remaining modules, classes, and methods that do not have them