Support for URLs with query string value on IE > 9

On Internet Explorer > 9, if the URL contains some query string value the request URL will be wrong, because of a bugged edit due to `urlWithParams`, which manipulates the URL in order to add some query string values, such as `evs_buffer_size_limit`.

For example, `new EventSource '/?ciao=ola'` produces a request to `/?ciao=ola?evs_buffer_size_limit=262144`; note the double `?`, which produces the wrong query hash `ciao => ola?evs_buffer_size_limit=262144`.

This edit fixes it using the property of virtual anchor tags of parsing URLs in order to safely manipulate the URL.