Add DIY Fork Development Setup

I added a DIY development setup for anyone who wanted an alternative to the Virtualbox, Vagrant, Ansible route. This is the environment I use to create my blog posts and figured others would find it useful
This assumes a system install of `rvm`, which is actually not recommended. How about:

```bash
$ sudo ln -s $(which jekyll) /usr/local/bin/jekyll
```

That feels ugly, though. I suspect the real solution is to remove the build scripts' hardcoded path and rely on `$PATH` instead. @ycombinator, is there a reason `build_script.sh` references jekyll like that?