[fix] If the CSS and JS is already loaded, we should still execute the callback.
[fix] The first argument of a `each` call should always be value.
[minor] Added a collection#array method to transform values in arrays.
[major] Added an async#each method.

This async#each method is different then most known iterators. It's loosely based
Zoidberg, a flow control library that I'm writing for Node.js. It features an
options argument that can be used to fine-tune the async methods. This can contain
the context of the callbacks as well as a execution timeout.