tox: Update pytest-qt to 1.6.0.

- Reduced verbosity when exceptions are captured in virtual methods.

- `pytestqt.plugin` has been split in several files and tests have been
  moved out of the `pytestqt` package. This should not affect users, but it
  is worth mentioning nonetheless.

- `QApplication.processEvents()` is now called before and after other fixtures
  and teardown hooks, to better try to avoid non-processed events from leaking
  from one test to the next.

- Show Qt/PyQt/PySide versions in pytest header.

- Disconnect SignalBlocker functions after its loop exits to ensure second
  emissions that call the internal functions on the now-garbage-collected
  SignalBlocker instance.

tox.ini

@@ -18,7 +18,7 @@ deps =
     py==1.4.30
     pytest==2.7.2
     pytest-capturelog==0.7
-    pytest-qt==1.5.1
+    pytest-qt==1.6.0
     pytest-mock==0.7.0
     pytest-html==1.6
     hypothesis==1.11.0