Update to Jruby-1.7.3 and processing-2.0b8

I'm not sure how long processing-2.0 is going to remain in beta stage, but this is a big update since processing-2.0 includes many changes that are not backward compatible (with processing-1.5.1). Further changes have been made inline with the now default ruby-1.9 support with jruby-1.7.3.