Support specifying requests timeout

[rectalogic]

By default requests does not use timeouts, so it can hang forever. Production code using requests should almost always specify a timeout.
http://docs.python-requests.org/en/master/user/advanced/#timeouts

I can subclass oic.oic.Client to forward a timeout for most of pyoidc requests usage:

class Client(oic.oic.Client):
    def http_request(self, *args, **kwargs):
        # Set requests timeout for all http connections pyoidc makes
        kwargs["timeout"] = (3.05, 10)
        return super(Client, self).http_request(*args, **kwargs)

But pyoidc fetches keys without specifying any timeout or using the above Client to make the request, see KeyBundle.do_remote
https://github.com/OpenIDC/pyoidc/blob/master/src/oic/utils/keyio.py#L168