Use defined?(JRUBY_VERSION) instead of RUBY_ENGINE
Use defined?(JRUBY_VERSION) instead of RUBY_ENGINE

Fixes #149

pressrelations/bunny,wconrad/bunny,teodor-pripoae/bunny,0xfaded/bunny,0xfaded/bunny,gferguson-gd/bunny,teodor-pripoae/bunny,jafrog/bunny,gferguson-gd/bunny,jafrog/bunny,bartj3/bunny,wconrad/bunny,bartj3/bunny,pressrelations/bunny