Add NumericValue.to_float()
Purity, source order, and comments.
Use (Token, Option<ParseError>) uniformly in the tokenizer.
Quirks mode is indeed ASCII case-insensitive.

See https://dvcs.w3.org/hg/csswg/rev/2c3f78d97b93
For loops are nice too.
Have consume_primitive() take a token parameter.
Make stuff public, adjust naming, add Invalid{Declaration,Rule}
Add UNTESTED tree construction for declarations.
Better test failure reporting
Add tests for unitless rect() quirks mode
Tests and fixes for declarations