Fix for issue #3: Tests should automatically take latest rhino file

This commit fixes #3 by:

1. Adding a hook to run Grunt tasks from Gradle
2. Adding a hook to get package information from package.json
3. Adding a task to Grunt to build the latest version of rhino
4. Updating the Gradle build to run 3 before tests
5. Updating the Gradle build to use 3 when testing