Updated site to promote the Git book.

I updated the Contact page to reference a medium sized picture of
the [Learn Git in a Month of Lunches](http://www.manning.com/umali/) book.

I also updated my "tech" tab to link to the book as well. Hurray!
Merging 'master' to this amended commit.

I had pushed up an amended commit (5a1db55)! But now I want to replace
that.