Replaced regexp lookahead with two regular expressions

Idea is that I replaced
"^(?!-*(?:expression|(?:moz-)?binding))(?:[.#]?-?(?:[_a-z0-9-]+)(?:-[_a-z0-9-]+)*-?|-?(?:[0-9]+(?:\\.[0-9]*)?|\\.[0-9]+)(?:[a-z]{1,2}|%)?|!important|)\\z/i"

regexp with:

"^(-*(?:expression|(?:moz-)?binding))" (it should not match)
"(?:[.#]?-?(?:[_a-z0-9-]+)(?:-[_a-z0-9-]+)*-?|-?(?:[0-9]+(?:\\.[0-9]*)?|\\.[0-9]+)(?:[a-z]{1,2}|%)?|!important|)\\z/i" (it should match).

Probably it's good idea to look on second commit only. As first one is just "go fmt". Tests pass now.