Rewrite README in RST

Change-Id: Ia0a51a4d971e5bb74555cdf6fb316f31e389b48b
Update search_keywords example to match current API

Change-Id: I9a8971d5af73b73e1e77ea692984d6148170a6b3
Beef up README

Change-Id: Iafe59af419fbb6ba6e7a9e537dd35a0d5beefc04