bump version in readme

Change-Id: Ia527f223c161ccbcc5912086706936935ba3e652
Reviewed-on: https://review.couchbase.org/c/CouchbaseMock/+/193750
Tested-by: David Nault <david.nault@couchbase.com>
Reviewed-by: David Nault <david.nault@couchbase.com>

Author: dnault

README.md

@@ -33,7 +33,7 @@ Once the mock has been started, it may be used like a normal Couchbase server,
 with clients bootstrapping over HTTP using the port specified as `--port`.
 
 ```sh
-java -jar CouchbaseMock-1.5.26.jar --port 9000
+java -jar CouchbaseMock-1.5.27.jar --port 9000
 ```
 
 and then in another console: