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
updating changelog
Merge branch 'master' into update_changelog

Conflicts:
	CHANGES.txt
Merge pull request #83 from enthought/update_changelog

Updating the Traits changelog
Close docstring in sample code to fix Pygmentation error
comment cleanup
minor grammar correction
Added 'self' to member functions
Fixed PEP8 compliancy
Improved PEP8 compliancy of Line2D example in user manual.
Merge pull request #86 from enthought/minor-fix-example

Minor fix for event.py example in user manual