Improve deployment toolchain

Add emberjs.com style deployment tasks from the ember.js website
project. Basic style is as follows:

* Work is performed on the `website` repo
* Middleman functions as normal
* Build directory is ignored
* Two new rake tasks are added: `build` and `deploy`
* `rake build` just runs the middleman build but provides a way for us
  to hook in custom tasks that need to be run during build.
* `rake deploy` does the following:
  - Asks for a deployment message
  - Creates or uses the build directory
  - Initializes the local repo if needed and points the remote to the
    `probablywrong/probablywrong.github.io` repo.
  - Updates to origin/master
  - Removes all the files
  - Builds the site
  - Adds all the files with the previously entered commit message
  - Pushes to the site repo
* This workflow has been enhanced to allow for a RESET env var to
  signify that the local repository should be completely deleted,
  refreshed from origin/master, and force pushed to the site repo.