Fixing JSBin

Hi there!

From what I've seen the program has two problems:

1. When you don't have `.css` or `.js` files, the `final` array does have an element of an empty string which causes that the async queue couldn't be completed.

2. The jsbin url parsing wasn't working... I've read the documentation of jsbin and it seems that the best way to get is to fetch the `/quiet` version. This is the only case in which I've seen the script failing within the examples.

If you do find other cases let me know because maybe I didn't noticed.

PS: I created a `tmp/` folder inside the application to be more OS compatible, working fine on my Mac machine but not on my Windows one. Now it should be working in both :smiley: