Dynamically inject spec iframes into the document 

These changes aim to improve the loading of large test suites with a lot of dependancies.

I'm not sure how widespread an issue this is but I'm currently refactoring a project that has to load a large number of dependancies per spec. In total the full suite transfers about 8mb of data and takes about 2 mins until the document is loaded (ie. all iframes have loaded too). This causes often causes Phantom and sometimes even Chrome to become unresponsive.

The solution involves dynamically inserting one iframe (spec) at a time, waiting until it has loaded and then proceeding to the next one. This means the time until initial page load is very fast (the actual time until the specs are all ready is about the same) and the load on the server is staggered.