Rework (default) init.d script, again

* Store environment variables in /etc/sysconfig/kafka. Might be blasphemy to use 'export' in these files, but I haven't seen anything about it though.
* Source /etc/sysconfig/kafka in init.d script.
* Try to stop kafka by sending a SIGINT and then TERM&KILL. The stop script that is bundled with kafka uses SIGINT, so why not.
Correct configure spec w.r.t to new init.d script layout
Add init.d script for the debian platform
Add debian to supported OSes
Exit with status 3 if init.d script is called with unknown action(s)
Add RSpec configure block to source integration spec_helper
Add sysconfig file for zookeeper recipe
Move attribute overrides to platforms section in .kitchen.yml

Java 7 for CentOS and Java 6 for Debian. For some reason Java 7 won't
install properly on Debian.
Update README w.r.t. the debian platform

[ci skip]
Merge branch 'debian-support'