Update CHANGELOG.md and Trapperkeeper dependency for 0.5.2 release

This commit adds notes to the CHANGELOG.md for the forthcoming 0.5.2
release.  This commit also updates the dependency on the Trapperkeeper
package to 0.4.2, the latest Trapperkeeper release as of this commit.
Merge pull request #32 from camlow325/0.5.2-release

Update CHANGELOG.md and Trapperkeeper dependency for 0.5.2 release