Add test case for SPY-146.

This changeset adds a test case to make sure observe with 2-byte
UTF-8 chars works as expected. To pass, this requires at least
spymemcached 2.10.3 in place.

Change-Id: I91b629f3a69d2c5587d2ea7be5261ed015d8e6e6
Reviewed-on: http://review.couchbase.org/30702
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>