Add unit tests for `HasTraits.sync_traits`
BUG: Add __init__.py files for all tests/ directories.
Add further sync_trait tests
Merge pull request #111 from enthought/fix-add-__init__

BUG: Add __init__.py files for all tests/ directories.
ENH: Remove traits.util.refresh.
Merge pull request #113 from enthought/fix-remove-refresh

Remove traits.util.refresh
Improve docstring of `HasTraits.remove_trait`.
Add tests for `add_trait` and `remove_trait`.
Remove unused trait definitions in test.
Improved unit test for deleting a synchronized trait
Merge branch 'tst-improve-coverage-hastraits' of https://github.com/enthought/traits into tst-improve-coverage-hastraits
Fix typos.
Fix test for deleted sync trait.
Merge pull request #114 from enthought/tst-improve-coverage-hastraits

Unit tests for HasTraits class
Merge remote-tracking branch 'origin/master' into fix-madness-in-method