Include ant CompileTask in maven jar to fix issue 121

Fixes issues #121 

To verify this fix, simply run mvn clean install, then use the produced jar in an ant build file to be able to run CompileTask.

    <taskdef name="closure" classname="com.google.javascript.jscomp.ant.CompileTask" classpathref="/path/to/jar"/>


Ping @jpitz to review