Fix/trainvm 17

+ Fixes: https://jira.puppetlabs.com/browse/TRAINVM-17
+ The bootstrap process uses Puppet 3 now!
+ Download the .asc signature and verify integrity of download - resolves #92
+ Allows you to delete the built and packaged VM - to avoid the problem of adding to the zip file instead of creating a new zip file
+ Updated list of cache modules to now cache the latest versions.