Mercurial book

[iris clark]

Hi, Lars.

> In this chapter:
> http://openjdk.java.net/guide/repositories.html#installConfig
> 
> Perhaps you could include a link to the free book about Mercurial?
> http://hgbook.red-bean.com/

An obvious improvement.  No idea why I didn't do that when I wrote
that section, perhaps because I'd already included a reference in the
intro to the entire "Repositories" section?  Regardless, the reference
clearly needs to be added here too.

I'll push this (and any other changes I've made) late this week or
early next.

Thanks,
iris