Woah -> Whoa

Gradle can be run directly on Mac/Linux/Windows and
auto-download dependencies (much like sbt for Scala),
as well as simplify IDE integration.

Add appropriate .gitignore for this sub-tree.

For developers, to add a new exercism:

    cp -r _template new-exercism
    # create test in new-exercism/src/test/java/SampleTest.java
    git add new-exercism

Users will be able to just run "./gradlew check" to run tests.

This is the complete skeleton for enabling Java, from curriculum
through the first exercise. Java is listed in the main curriculum.rb
but commented out; we will activate once there are a sufficient body
of exercises ported.

The java.png icon is taken from http://findicons.com/icon/88943/java?id=89126,
released under a freeware license.

Describe how to minimally set-up Java and JUnit. (Future work may
try to see if we can get Locale.additional_files working and provide
build integration via Gradle or Maven.)

The BobTest is a straight up port of the Python Bob.

This starts the path of fixing #933.