Bumped version

Managed to mess up pushing to rubygems and so need to version bump as it
is not possible to overwrite an existing version.
Update version in Gemfile
Added plugins

Will now load any installed gem beginning with the_dude- as a plugin.
Improved the undefined variable error message
Added console test helpers

Added some test helpers to make it easier to output debug code.
They are included before the_dude so that they can be used everywhere.
Added TheDude.command method

Added a method to find a command by its original expression. This was
needed because in the commands hash they are stored by processed regex
to make them easier to iterate and match over.

This required some refactoring of expressions in order to store both the
original and processed expression.