Build without dependencies

Refactor the build to exclude dependencies. This is required if a project already uses some of the libraries Abyssa depends on.

Borrowed and enhanced the build.js from the crossroads.js project.
Added package.json.
Introduced the license comment.
Changed the test runner to include the dependencies separately.
Fixed the README file's Dependencies section.

This pull request includes the previous one: [Add compatibility with Uglify v2](https://github.com/AlexGalays/abyssa-js/pull/2)