add support for //include

[justone]

This change adds support for including dotjs scripts. For example, given the following files:

foo.js

alert('foo');

bar.com.js

// include foo.js

Then fetching the js for bar.com would result in:

// include foo.js
alert('foo');

This sort of addresses #27.

[stroborobo]

I like this. It's nice for including libraries since you can't use $.getScript().
+1 :)

[justone]

Rebased to master.