Add a C version of bob-walker

Claims that the Go version of bob-walker can now be tested, by comparing
to this C implementation. To run through the 3 word list 1 million times
in C takes 0.31 seconds. With the 5 word list in sport mode, this takes
only 0.51 seconds.

Beat that Hipsters!

(Yes, I'm aware that this is probably extremely bad C, but this has
never stopped me writing code before, nor will it stop me in future)
Clarify the background of this project

To an outsider this project might look like some kind of mean-spirited
urine extraction. I wanted to make clear what the background was and why
we keep adding to it, just so that people don't get the wrong idea.
Suggestions from #11
Merge pull request #15 from dcarley/clarify-background

Clarify the background of this project
Merge pull request #12 from dcarley/c-walker

Add a C version of bob-walker
Add bob-walker.py

Through an amazing oversight, we have not yet created a bob-walker in
Python. This Pull Request attempts to address this egregious error using
something that one hopes will become the reference implementation of a
bob walker.

This implements all the modes available in the Perl version, with three
notable new features:

    - If bob is being drunk and random, the amount of slurring varies. This
      makes it possible for bob to be drunk AND consistent which should
      be an allowable state.
    - bob will only say one million words before he gives up. If you'd
      like him to stop earlier, then just press CTRL-C at which point
      he's going to suggest that it might be PUB TIME!
    - If bob encounters an error, we don't care. We're just going to
      stop what we are doing and suggest having another pint. This
      probably won't stop the error occurring, but we can always fix
      that later.