Rendering nested properties.
Fixed nested rules nested more than once.
Fixed the rendering of nested rules without any properties.
Parent selector replacement.
Comments still work too.
Style cleanup.
Renaming some types and added a few descriptions.
Removed ampersand as a discrete token (just a symbol) and moved where the token transformations take place.
Restored the property expression tests now that the minus sign lexes properly.
Surprisingly, the semi-colon-less property test works.
Reorganized the test files to match the implementation file structure.