Autoconf tutorial updated

[Edward Rosten]

Hi All,

When I first started using Autoconf, I found it hard because there wasn't
any good "getting started" documentation. So, I wrote a tutorial on it.
Since I don't want to be responsible for out of date information and
propagating misinformation and bad habits, I updated it.

It's now on github here:

https://github.com/edrosten/autoconf_tutorial

I think documentation works well as a collaborative effort and the first
version certainly had some howlers in it, so I invite anyone to let me know
of errors, bad habits or things I've missed.


Regards

-Ed