Add HTTP broker, one-off event submitter, general Go support

Overview:

- Add HTTP broker that caches irregularly submitted events, and submits them to Flapjack as a heartbeat.
- Add simple CLI tool for submitting one-off events to Flapjack.
- Add basic Go libraries for handling events, and sending events to Redis.
- Add basic GLI support for `exec`ing subcommands via the command line.
- Add build script for building components written in Go.

Developer [documentation](https://github.com/flapjack/flapjack/wiki/DEVELOPING) has been [updated](https://github.com/flapjack/flapjack/wiki/DEVELOPING/_compare/882bd2fe25bdf702ec4fe8eecd0dcb9249a1dae5...6c6f387c937d8b64137301cdf51e95fa41a55a5f).