[#69457338] Checkpoint

* Ping-pong based websocket listener for TC ↔ Loggregator communication
* Multi-loggregator-server-capable TC HttpHandler that returns multipart/x-protobuf

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>
[#69457338] Clean up http_handler_test

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>
[#69457338] Make trafficcontroller.HttpHandler a http.Handler

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>
[#69457338] Use HttpHandler for /recent

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>
Merge pull request #21 from cloudfoundry/69457338-http-recent

69457338 http recent