CTM Example: use a more compatible script loading technique

Use `insertBefore` instead of `appendChild` to load JavaScript from the build service, like all most popular script loaders do (Google Analytics, Twitter widgets, Facebook like button, Disqus comments…).

Also puts it into a self executing anonymous function, which should be much safer than having it in the global scope.

/cc @triblondon 

![ ](http://gifs.joelglovier.com/hubbers/hubmojis-furyus-wink.gif)
Could be `document.scripts[0]` nowadays. See <https://mathiasbynens.be/notes/async-analytics-snippet#var>:

> **Note:** If support for Firefox < 9 and BlackBerry OS 5 is not an issue, you could just use `document.scripts[0]`.