Aligned project with Underscore/Lodash

- I updated the documentation so it was easier to digest
- I updated the folder structure so that methods that were previously in `/src/__/chaining` are now in `/src/__/functions` simply because they are not necessarily chainable methods... yet
- I aligned the project with Underscore/Lodashes documentation, in that this repo is not aiming for feature parity with either library, but that those features will ultimately be supported as it is improved
- I added the `now()` method
- I updated the `flatten()` method, so it is now 1:1 with Underscore's implementation and actually supports the `shallow` argument.