Create a distribution script.

Publishes a previously released version to npm and prepares an archive for
upload to GitHub and CDNs.  This distribution archive is different than
a regular release archive because it only contains the distribution files
(i.e. the `dist` folder).

Closes #152.
For some reason you can't comment on lines that haven't changed. :octocat: :whale:  
You can remove the lines above that deal with checking if npm and node are installed because they are no longer used in this script.