Update to Jruby-1.7.4 and processing-2.0

Processing-2.0 has just been released. This is a big update since processing-2.0 includes many changes that are not backward compatible (with processing-1.5.1 notably P2D and P3D become jogl2). Further significant changes have been made inline with the now default ruby-1.9 support with jruby-1.7.4. Anyone interested in maintaining processing-1.5.1 compatibility should make their case soon.
@moumar, @jashkenas