Updated demo page shows many versions and configs

_Replacing PR #225 with this so I can free up my `gh-pages` branch._

I updated the demo page to add a dropdown to show/test out various versions and configurations:
 - Stable version (currently 1.1.7) with the traditional (global) export
 - Beta version (currently 1.2.0-beta.3) with the traditional (global) export
 - Beta version (currently 1.2.0-beta.3) with the AMD export
 - Edge version (current git master) with the traditional (global) export
 - Edge version (current git master) with the AMD export

In order to not make a bunch of duplicate files that all needed to be updated when we rev our versions, I made the JS files uglier than I would've liked and not really following best practices :broken_heart:.  However, this allowed me to centralize all of the versioning info for the demo page into a DRY set of HTML elements (see the `#versions` element), which I :heart:.

You can see it live on my ZC `gh-pages` branch: http://jamesmgreene.github.io/ZeroClipboard/