add matplotlib to prerequisites
add matplotlib to prerequisites

Change-Id: I9878ddeec90b9d275e6e132afce276dc7b076382
Reviewed-on: http://review.couchbase.org/24868
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>

pavel-paulau/cbagent,mikewied/cbagent,couchbase/cbmonitor,ronniedada/litmus,ronniedada/litmus,couchbase/cbagent,vmx/cbagent,couchbase/cbmonitor