Fix precedence of conditional blocks (+API redesign)

Implement @supports.

Draft interpretor for @supports.

Media queries: fix popping two items off stack.

I forgot that FIFO reversed the order of the list.

Implement @import & @media

Dependency injection required for an HTTP client library.

Fix syntax errors in ConditionalStyles

Support multiple @document conditions (FIX)

Switch @document from conjunctive conditions to disjunctive conditions.

Implement @document rules (save regexp() conditions).

I've still got to select a regexp library to power it.