Fixed compatibility with multiprocess plugin

* Reworked printing inline timings;
* Used multiporicessing.Manager dict for test timings to share
  time results between processes;
* Used static variable for test timings (since the multiprocessing
  plugin instantiates this plugin several times);
* Used monkeypatch for TestResult instead of creating new instance;
* Updated unit tests.
Merge pull request #42 from skudriashev/multiprocess-fix

Fixed compatibility with multiprocess plugin