Merge pull request #47 from grosser/dry

dry
Updating changelog for 0.6.1 release.
Version bump to 0.6.1
Moving all classes under the PreCommit namespace.

Changed the `PreCommit` class to be a module instead.

There are some indentation changes in the patch, however no
functionality has changed. Each test passes when run individually
as well as the entire suite when run together.
Merge pull request #49 from jish/namespaces_are_cool

Moving all classes under the PreCommit namespace.
test cleanup and integration testing
load pre-commit in a consistent way - fix travis
execjs needs nodejs