Add bob-walker in brainf--k

This is an MVP of bob-walker implemented in the ever popular brainf--k
programming language. As soon as I can work out how to pass in flags to
Brainf--k I will of course add sport mode.

- It accepts no arguments
- It runs through the three words 10 times rather than infinitely

Patches as always are welcomed...

You may find [this](https://github.com/garretraziel/mindfuck) quite
helpful.

```
$ ../mindfuck/mindfuck.py bob-walker.fk
beer
beard
pie
...
```
Sort implementations in the README
Add sport mode to bob-walker.fk for a Dan Carley MVP

Joyously you can either run this in mode 0 (normal) or mode 1 (sport).
Because I'm feeling quite nice, I've also added a
docs/bob-walker-explained.fk which tries to expand line by line, should
your brain need unf--king.
Merge pull request #10 from dcarley/brainf--k

Add a minimal bob-walker in brainf--k