Validate/update doc strings and README

[PhillSimonds]

The following need to be updated/written for this issue to be considered resolved:

• [x] README.md at root of repo
• [x] docs/configuration.md
• [x] docs/mapping_schemas.md
• [x] docs/validate_command.md
• [x] docs/ansible_command.md
• [x] docs/schema_command.md
• [ ] docs/using_jsonschema_refs.md
• [x] Update Doc Strings

[PhillSimonds]

Doc strings have been updated to adhere to pydocstyle, but there are still some instances where pydocstyle isn't catching undefined arguments or unclear input types (e.g. one of the docstrings discusses that the argument should be a string, then later it says it should be a list). I've unchecked the Update Doc Strings todo above so that we can make sure the settings for pydocstyle are set correctly, and go through the doc strings with a little more detail to ensure they are all correct.