Use bundler to build gem instead of hoe. Fixed deprecated calls to import_class.

Chad, 
    I'm using this gem and I'm trying to get rid of annoying deprecation warnings after upgrading to JRuby 1.7 (import_class -> java_import). I was having a hard time finding the correct version of hoe to build the gem, so I switched it to build using bundler. Also, it looks like version 0.1.5 was never pushed to rubygems, even though it exists on the Rubyforge jruby-extras page, so I updated the version number to 0.1.6.