Add a list of two-tuples to the uri query components.

def add_params_to_uri(uri, params, fragment=False):
    """Add a list of two-tuples to the uri query components."""
    sch, net, path, par, query, fra = urlparse.urlparse(uri)
    if fragment:
        fra = add_params_to_qs(fra, params)
    else:
        query = add_params_to_qs(query, params)
    return urlparse.urlunparse((sch, net, path, par, query, fra))