ref #1554 [Implement in-memory content cache for the producer]

http://redmine.named-data.net/issues/1554
ref #1555 [Workaround for missed frames]

http://redmine.named-data.net/issues/1555
'issues/1555-skip-frames' -> 'dev'
'dev' -> 'issues/1554-in-memory-cache'
ref #1555 ref #1554

- fixes
'issues/1554-in-memory-cache' -> 'dev'