Clean up README file
Clean up README file

This makes the README file much more concise and too the point.  It generally directs the user to the official website, but also includes a few useful pointers at well to help them get started.

Signed-off-by: William Vaughan <1730ac11c5151f6e435009b3b26edbbf6f9f2244@linkedin.com>

apache/incubator-datafu,shaohua-zhang/incubator-datafu,apache/incubator-datafu,shaohua-zhang/incubator-datafu,apache/incubator-datafu,shaohua-zhang/incubator-datafu,shaohua-zhang/incubator-datafu,shaohua-zhang/incubator-datafu,apache/incubator-datafu,apache/incubator-datafu