Make dependency on Underscore / Lodash explicit

[neemzy]

When trying to use the library, I'm getting:

ReferenceError: _ is not defined

I don't see this anywhere in the docs.

Ideally, you may consider publishing this on NPM and/or Bower, which would allow dependency specification (Underscore or Lodash, and anything else needed would be installed along) and, in the case of the former, would allow the library to be usable without attaching itself to the global scope (with minimal code changes).

Thanks!

[Rykus0]

Or better yet - remove the dependency. I see only 3 instances where it's used, but isn't really needed. If I'm able to, I'll send a PR with it removed.