Merge branch 'master', remote-tracking branch 'upstream/master'
Added ClientThreadsRespected.
Added more tear down tests.
Better comments phrasing.
A safer test.
And another minor touch to comments and construct.
Starting the refcount from 1, not 0.
Made use of std::atomic-s.
Merge pull request #40 from dkorolev/master

Added the ClientThreadsRespecter sync primitive.