README.md: new copy of README; convert to GitHub flavored markup.

The addition of this file makes it easier to read the github.com
project pages.

Change-Id: Ibb08e431fcbceae5b8692f6bc170c90369d9e159
Merge branch 'add-github-flavored-readme'

Change-Id: If25ac46e4baafaf5fcf32b1ca861039f74bb356e