Add a utility method to load data from a yaml file

We're doing this pretty often, so in the spirit of reuse, we add a method to
handle loading yaml files.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Add test Rakefile. Remove before going into prod

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Add a Build class

This commit adds a Build class to the packaging repo. The Build class is the
beginning of a shift to using more encapsulated, easier to follow logic in
packaaging. It offers us the opportunity to track state much more easily than
before. The new Build class contains instance variables for all of the
packaging repo's many tracked data, as well as functionality to load these
variables from yaml files, return them as a hash, and most importantly, write
them back out to yaml. This will allow us to cease using a mess of environment
variables when issuing remote commands. Instead of having to constantly update
which params are sent as environment variables to remote tasks, this allows us
to send the entire state of the build object along with our desired build task,
preventing much of the trial and error of the current approach.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>