Add a short description to the home page

[mlevison]

To a stranger, outside of the Agile cognescenti the current home page is intimidating :-)

[rkasper]

Hi, Mark! I love the idea. What do you think it should look like? Will you propose something? Be well!

[mlevison]

Why pare down the intro to your book? I've not seen it (sorry), however I assume you give the person on the street an intro.