Checkpoint commit working on REST API

This is a temporary commit. The current version is mostly
wrong, but it will serve as a base for the final solution.

TODO:
* Use a []byte channel to send data from the Listener to the
  AMQP workers, and do the marshalling in the Listener
* Add the possibility to send the message using JSON at least
  for debugging purpose
* Reduce some overhead, since at the moment we're probably doing
  some extra conversions that could be removed
Use a []byte channel for AMQP workers

Move to a []byte channel for sending messages to AMQP workers,
keeping the details of it opaques for them.
Use Google's Protobuf for marshaling messages
Fix a bug in logger interface

The way variadic params were passed around was plain wrong.
Fix it accordingly to the specification:
	http://golang.org/ref/spec#Passing_arguments_to_..._parameters
Fix logging usage
Update TestResults structure

Add a fiel called TestData, that will include the actual test data.
Also, add the output of the protobuf compiler for convenience.
This last point might change in the future.
Handle TestData field in listener
Merge pull request #11 from piffio/issue-10-rest-api

Issue 10 rest api