Initial commit of CouchDB client without integration to YCSB

Checking in the client and README file. The client uses LightCouch
and slf4j. The README includes instructions for using the client with
the required database.
Integrate CouchDB client with YCSB

Include couchdb in the list of supported data bases and include class name
Change Maven build target to include CouchDB. Set version number to LightCouch
supported version number
Update couchdb pom.xml to be consistent with other bindings
Create an exception from building the unit tests because they require
CouchDB to be running.
Using log4j instead of Nop logger for slf4j. Nop logger was logging to stderr
Change .gitignore to /*/target/ to exclude all targets in git status