Refactor event validation to use errors package
Add fixme
Remove ability to emit the same event. Be a better cli citizen.

 - Remove looping logic (not much use submitting the same event every
   time).
 - Use flapjack.Transport for working with Redis.
 - Handle errors more consistently, exit with non-zero return code
   appropriately.
Extend build.sh to build httpbroker, run tests
Switch to kingpin for cli arg parsing.
Provide better debugging output.