CBIDXT-117: added an index definition for beer-sample.

Change-Id: I3c8f3707c59b2e0ec59d0a8c18db0fb8b5484b1e
Reviewed-on: http://review.couchbase.org/39939
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>