Add Requirements, Install instructions, and link to documentation into readme.md

Forgive me in advance if I get the etiquette wrong here, this is my first pull request. I've fleshed out the `readme.md` file and added the requirements (poached from the Anchor site documentation) and a slightly rephrased version of the install instructions (worth noting, the reference to the directory "`contents`" in the website install instructions should actually be "`content`"). The aim here is simply to help people who happen across the repo to deploy/test out Anchor quicker and easier.