Explore decreasing the production file size

[munro]

Self could use underscore as a dependency, though not everyone is as partial to underscore as I am. Underscore provides a _.extend, which I have to implement inside Self.

Currying may also be helpful in decreasing the file size, except the problem with underscore's currying is I have to bind the scope, which Self does not do, so _.bind may not be that helpful.

I will probably release a self-underscore file for those who want to use underscore.