Update CHANGELOG.md

v0.1.1 (January 4, 2014)
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* Documentation improvements.
* Basic testing via UnTest: https://github.com/tenpn/untest
* Fixed: ShuffleBag now correctly removes items as they are used.
* Fixed: Vector3.WithY() was returning bogus vectors.
* Feature: Vector3.Approx(), currently used for internal testing.