Stop disabling logging plugin

Thanks to the adjustments in pytest-dev/pytest#3124 we don't need to
worry about live logging with a low logging level being enabled by
default in `pytest` any more. Go back to using the default plugin set.

.travis.yml

@@ -30,4 +30,4 @@ install:
 
 # NOTE: no support for pandas/pytables yet
 script:
-    - pytest --use-docker tests/ -p no:logging
+    - pytest --use-docker tests/