Fix cyclic garbage created by use of WeakRef; add some WeakRef tests.  Fixes issue #95.
Tweak test; remove debugging print statement.
BUG: Return a true `set` in `TraitSetObject.copy()`

Otherwise, an uninitialized TraitSetObject is returned, and operations on it
will fail.

Fixes #97.
Add changelog entry.
Merge pull request #98 from enthought/fix-set-discard

BUG: Return a true `set` in `TraitSetObject.copy()`
Merge pull request #96 from enthought/fix-weak-ref-cyclic-garbage

Fix cyclic garbage created by use of WeakRef; add some WeakRef tests.
Add changelog entry for PR #96 (issue #95).
Merge pull request #99 from enthought/update-changelog

Add changelog entry for PR #96 (issue #95).
Merge remote-tracking branch 'origin/master' into fix/adapter-init-sequence
Mention PR number instead of commit number in CHANGES.txt