Add GET-parameters to URL. If parameters are exist then they will be changed.
        url - URL, string value
        params - dict {'GET-parameter name': 'value'}

def change_url_query_params(url, params):
    """
    Add GET-parameters to URL. If parameters are exist then they will be changed.
        url - URL, string value
        params - dict {'GET-parameter name': 'value'}
    """
    url_parts = list(urlparse.urlparse(url))
    query = dict(urlparse.parse_qsl(url_parts[4]))
    query.update(params)
    url_parts[4] = urllib.urlencode(encode_url_query_params(query))
    return urlparse.urlunparse(url_parts)