* Start implementing a query API for go using net/rpc
* Use a conventional JSON POST API rather than go net/rpc
net/rpc doesn't automatically handle reconnecting and we have better
logging and metrics infrastructure for monitoring HTTP apis.
* Implement the query API and add it to the integration tests
* Increase the timeout, travis seems to be a bit slow
* Clarify that state events are the things that are not returned if they are not requested
* Add utility function for converting arrays of numeric event IDs to pq Int64Arrays
* Warn people against requesting empty state keys by accident
