couchstore.py: Allow CouchStore objects to disable io buffering
couchstore.py: Allow CouchStore objects to disable io buffering

Add the optional 'unbuffered' flag to CouchStore __init__ method,
which allows iobuffering to be disabled.

Change-Id: I2f56617ade4fc04f8251d3ff99fd2e77d111dc32
Reviewed-on: http://review.couchbase.org/73055
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Will Gardner <5d7e5a4e8e63c739e07f011adf51f2e51dd3ec09@rdner.io>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

couchbaselabs/couchstore,couchbaselabs/couchstore,couchbaselabs/couchstore