Add full_name to the @modules

Currently, the :name attribute of @modules was
only the name of the actual repository and not
prefixed with the account (as per the Modulefile
format).

This commit adds a second attribute called full_name
that contains both.
Add module helper methods

This commit adds two helper methods for the
stored @modules.

modules - allows users to directly access the
modules queried out of a Puppetfile

clear_modules - clears all modules. this is added
to support use cases where a user may want to
parse multiple puppet files in the same run.
add forge method

this commit adds a forge method for compatibility
with the Puppetfile format.

The method does not do anything, yet..
add print_output param to system_cmd

this commit adds another argument to system_cmd
called print_output. Currently, the output of
commands is returns if verbose is set.

this option allows the output to always be printed
regardless if verbose is set.
Merge pull request #11 from bodepd/helper_methods

Helper methods