Added an INTERVAL api call

This api call simply accepts a time in seconds. It'll pull all the
enabled modules every x seconds from then on and send them to the
client. It sort of supports milliseconds as well, but that is slightly
buggy atm.

Signed-off-by: Toon Schoenmakers <nighteyes1993@gmail.com>
Let's do builds on travis with and without debuggin

DEBUG() statements can break your code if you aren't careful,
how about we let travis detect this by doing both the builds.
They can essentially only break it if you do something like

if (1)
  DEBUG(255, "Oh yes that was true.");

A build without debugging would result into

if (1)

in that case, which would break it. Putting {}'s around it would
fix it.

Signed-off-by: Toon Schoenmakers <nighteyes1993@gmail.com>