adding Rakefile to install into gemsets.

requires the following:
 - gemset version
 - puppet version
 - hiera version
 - hiera-puppet-helper version

example:
rake install_into_gemset[ruby-1.8.7-p374@puppet-3.3.2,puppet-3.3.2,hiera-1.3.1,hiera-puppet-helper-1.0.1]