Changes for automated build process

This looks like more than it really is because of the two new modules.  Mostly it's just refactoring the build process and moving things around.

- Creates a new Rakefile that is used by the automated build process and updates README to reflect new usage.
- Fixes Vagrantfile and uses standard Centos base box
- Fixes gem caching to recognize pre-cached files from Vagrant or other build tools
- Adds local cache for PE & PE Agent downloads and puppetizes staging
- Implements epel module instead RPM based install
- Moves some of packer build scripts from another repo to be used for possible future packer build.
Bump to 4 Gigs, and add a note to the pdf saying, if you have less memory, lower the memory for the VM? Designing for optimal performance seems to be the thing to do, although we don't yet know how many people fall into the "don't have 4 free gigs" category.