Enable dist files to work with CommonJS AND amd-style/require.js

This PR is a proposition to make *handlebars.js* even more compatible with library styles. It add's compatibility to the [amd-style (require.js)](http://requirejs.org/) and includes #500 for building compatibility to CommonJS and not polluting global namespace anymore.

…or it might be a sign that *making compatible to* should find and end somewhere…