Version bump to 0.3.1.
Updated the copyright dates.
Revert "Merge pull request #64 from dekz/rake_task"

* This reverts commit 4334a11969a31b96751a6e0212f7e451bfb2801c, reversing
  changes made to b191595cd8d36c3ac5535d6176a627b612d50758.
* Let's hold this back until 0.4.0.