Starting to implement expressions.
Trying out a pratt-style parse setup.
Fleshing out the new parser a bit more.
Fixed parsing nested rules and compound selectors.
Got nested properties parsing again.
Restored comments.
Renamed some files and put assignment back in.
Got parent selectors parsing, though not evaluating (yet).
Replaced the old parser with the new one and started building an evaluator.
Starting to reimplement the CSS rendering.
Got very basic property expression evaluating and CSS rendering working again.
Got nested rules' selectors rendering again, but had to sacrifice a little immutability for the time being.
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.