allowing the 'ws-server' to process plain http GET requests

This is a port of the changes proposed in https://github.com/aphyr/riemann/pull/422

I've switched the uri's to /index and the 'q' parameter is now 'query' to be consistent with the existing websockets uris.

provides:
    GET /index
    GET /index/{host}
    GET /index/{host}/{service}

It's not 100% consistent yet, there is some work I need todo to retrofit some of the new helpers into the websocket handlers.

I figured the disclaimer in the doc of ws-server would get me out of jail for free.

I'll add a default order to least fix the ordering to host/service so that the results are consistent(ish) obviously will still need a disclaimer as we don't maintain some snapshot of the index to provided perfect consistency