automatically detect jruby

Author: denofevil

Diff for: config.yaml

@@ -17,9 +17,6 @@ server_start_up_timeout: 5
 # either should be on the $PATH or use full path
 interpreter: ruby
 
-# whether the interpreter is JRuby (XXX poll the interpreter for this info)
-is_jruby: false
-
 # whether to run JRuby instance in debug mode
 debug_jruby: false
 

Diff for: test-base/test_base.rb

@@ -75,7 +75,7 @@ def interpreter
   end
 
   def jruby?
-    config_load('is_jruby')
+    defined?(RUBY_ENGINE) && RUBY_ENGINE == "jruby"
   end
 
   def debug_jruby?