AptChef provisioner

This is 1/2 of #97 and addresses amination using Chef on debian family hosts.  I took a slightly different approach than @bunjiboys and would appreciate feedback.  

We'd like to have the yum-style Chef provisioner as well and would like to see if we can get to common model until we can figure out how to break the volume setup from the provisioning steps.  (see issue #102)  

There's also a change to environment.py that added a YAML view of the config in the log when amination starts so it's a bit easier to see what settings/values the plugins are contributing.

example usage:

aminate -B ami-abcdef --preserve-on-error -r us-west-1 node-base.json -i http://<your-local-apt-repo>/chef_10.26.0-1.ubuntu.11.04_amd64.deb -u http://<your-recipe-repo>/recipes.tar.gz -e ec2_apt_chef_linux

See the unit test for the example JSON file

/cc @bmoyles @mtripoli @coryb