Do not unescape urls on pushState

Before, this was happening:

History.pushState(null, null, "http://balupton.github.com/%23%2F/")
--> http://balupton.github.com/#//

If an encoded string is pushed explicitly, it should not be modified.
Merge pull request #282 from doits/fix_unescaping

Do not unescape urls on pushState