Fix typo in README.md

Changed 'Doker' to 'Docker'
Merge pull request #1 from phillipalexander/patch-1

Fix typo in README.md
Add container files for 12.04 through 13.10 Ubuntu
Add Debian 7 Dockerfile
Let's set the current containers the testing containers.

The `installed` containers will, additionally contain salt installed.
The testing images don't need the last step.