Feature/clean workspace cleanup

[hubert]

Here's the plugin for workspace cleanup (that i ref'd in the readme). I think it's worthwhile discussing whether we want plugins to be part of the gem or if they should reside in their own repos. Some thoughts on possible solutions:

• all plugins go in the gem. this would make installation a little easier and would address the discoverability of the issue.
• all plugins go outside of the gem. this would mean the individual plugins reside in their own repos. makes installation a bit more painful but also keeps the gem size minimal. we're saying the responsibility of the gem is just to provide hooks for plugins.
• maintain a core set of plugins and let more obscure plugins reside in their own repos.