Updating the README.

Don't need separate build instructions because the client is not built as
a part of bulding YCSB. The instructions mention Flux7 labs and Cloudant Inc.
Also list the default parameters and the parameters for running on the
Cloudant servers.
bugz id: 114. Exclude the CouchDB unit tests from running during a build

The unit tests fail on an exception if CouchDB is not running. Changed pom.xml
to exclude the unit tests. Include instructions in the README for reenabling
the unit tests.