add a test for the validate method
fix minor pep8 issues
update imports to not use the `api` module
fix issue #71
rename dict_test_case -> test_dict
Merge branch 'master' into fix-71

# By Pietro Berkes
# Via Pietro Berkes
* master: (27 commits)
  Update changelog.
  Improve documentation of 'ui' dispatch method.
  Update Travis CI files so we can test trait notification on UI thread.
  Pre- and post- change event notification hooks.
  Remove unnecessary assignment.
  Add a global trait change event tracer.
  Clean up imports.
  Improve docstrings.
  Refactor TraitChangeNotifyWrapper and ExtendedTraitChangeNotifyWrapper.
  Rename 'n' to 'arg_count'.
  Add missing call to `gc.collect()` to test.
  Cover `FastUITraitChangeNotifyWrapper` with tests.
  Cover `NewTraitChangeNotifyWrapper` for tests.
  The `dispatch='ui'` option has been broken since 2007, remove it.
  Test that objects with listeners can still be garbage collected.
  Cover `ExtendedTraitChangeNotifyWrapper`.
  Import unittest from traits.testing, remove unnecessary complications.
  Improve header.
  Cover the methods in TraitChangeNotifyWrapper with tests.
  Refactor: extract super class for static change notifier wrappers.
  ...
use unittest2 assert methods
added note about the `object is None` case
minor correction
Merge pull request #80 from enthought/fix-71

Fix 71