JsonRPC improvements

The PR contains patches, that make JsorpcRequestHandler compatible with [jsonrpclib](https://pypi.python.org/pypi/jsonrpclib):
* request id may be of any type (fixes #121)
* `error` is a dict with keys `code` and `message` (with fixes at `httpclient.JsonRPC` side)

I've also added support of `httpclient.fetch`'s arguments to `httpclient.JsonRPC` in order to support proxy, timeouts, etc.

By the way, thanks for Cyclone, it's awesome :)