Fix `urlFor` with regex

Before `urlFor` would return '/path/Hello\\.Josh' for a pattern
'/path/(:foo\\.:bar)' with parameters
`('foo' => 'Hello', 'bar' => 'Josh')`, when the expected return value
is '/path/Hello.Josh' (this test was introduced in commit cc722cc).

(Pull Request description updated (2013/09/26) because GitHub ate my \\)