Migrate to mailgun/route package for routing

@r0mant @russjones can you please review? This change migrates Vulcan library to use mailgun/route library
Should not you also enclose regexp in parentheses in case of multiple methods? E.g. now you get `MethodRegexp("POST|PUT")` but you should get `MethodRegexp("(POST|PUT)")` in order for it to be a valid regexp.