Py-md-doc

- Fixed: Can't find `:return` decorators (expecting only `:return:`).
- Fixed: Unhandled exception if there's more than one class in the file.
- Added: `social.jpg`

- Added: Special category `Ignore` to metadata. Functions in this category will be ignored.

- All functions that have parameters with default values now have two example code strings: a "short" example (parameters with default values aren't included) and a "long" example (all parameters with default values are explicitly assigned).
- Added default values to parameter table.
- Added: `parameter.py` to hold parameter information.
- Moved the documentation generation code for this module to `doc_gen.py` to avoid import path errors.

- Added support for class variables.
- Added much clearer code examples for function documentation.
- Added parameter types to the function parameter tables.