Add a query API to the roomserver for getting the latest events in a room. (#23)

* 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

vendor/manifest

@@ -98,7 +98,7 @@
 		{
 			"importpath": "github.com/matrix-org/util",
 			"repository": "https://github.com/matrix-org/util",
-			"revision": "ccef6dc7c24a7c896d96b433a9107b7c47ecf828",
+			"revision": "28bd7491c8aafbf346ca23821664f0f9911ef52b",
 			"branch": "master"
 		},
 		{
@@ -206,4 +206,4 @@
 			"branch": "master"
 		}
 	]
-}
+}