Refactor, work with cursor nesw, comments as whitespace, bugfix

[YairRand]

Per Krinkle's suggestion on splitting up the change for TTB support (#36) into smaller changes. Some refactoring, added support for cursor: nesw-resize; some support for /* comments */ within CSS statements (eg direction /* */ : /* */ ltr /* */;), and fixed a bug with URLs accepting keywords with immediately-following letters (see tests in "flip URLs when url transforms are on").