jubatus/jubatus — pull request #708 by kumagi (2014-03-05 06:23:48+00:00)
Title: don't mix when no update observed, fix #181

This PR is correspond to #181

If no update was done, we shouldn't invoke mix.

### discussion
Push_mixer should invoke mix without observing update.
Because every node should propagate update of others.
No node could detect the demands of mix without mix.