Moved redis, zmq, amq and mqtt to optional dependencies.
DEBUG=* for travis, as the tests blocks for some reason.
Setting debug env for real.
Readded hiredis, as it seems it is mandatory.
Adding libevent-dev headers to travis build.
Added libev-dev package to travis build.
Removed DEBUG flag from travis build.
Added QoS 1 for all subscriptions in MQTTAscoltatore.

Closes #36
Added QoS 1 for MQTTAscoltatore even during publishing.
Fixed QoS 1 support in case of exceptions.
Better test output formatting.
Benchmark performance fix.
Using node-uuid to generate a unique identifier.

Closes #27.
Fixed RedisAscoltatore without hiredis.

Closes #42.
Added the support for the connection of peers in ZeromqAscoltatore.

Closes #26.
Added some more semantic explanation in the README.

Closes #37.
Linted everything with JSHint. Added precommit hook.
Bumped to version 0.3.1. Updated HISTORY.md.
Fixed Mosca version at 0.2.0.
Bumped version to 0.3.2.