Add documentation on filter and populate usage

As mentioned in #72 I was going to send you the docs I wrote for the API I made with your module,
I've added them to the readme file. Let me know if you want anything changed
both mean the same to me, but I'm not a native english speaker, after looking up the rules it really just depends in what situation you use it, but it was a very small task to just change it to `less` so consider it done...