Try testing in JRuby 1.9 mode passing JRUBY_OPTS

For details read comments in https://github.com/jruby/jruby-rack/blob/master/.travis.yml

.travis.yml

@@ -1,13 +1,12 @@
 rvm:
+  - jruby
+  - jruby-head
   - 1.8.7
   - 1.9.2
   - 1.9.3
-  - jruby-18mode
-  # NOTE: seems to be failing on Travis the same way as jruby-rack did, stack 
-  # seems to overflow when gems are loaded (does not happen locally :() :
-  # SystemStackError: stack level too deep
-  # ./spec/../lib/warbler/traits/bundler.rb:30:in `after_configure'
-  #- jruby-19mode
 branches:
   only:
     - master
+env:
+  - JRUBY_OPTS="--1.8 --server -Xcext.enabled=false -Xcompile.invokedynamic=false"
+  - JRUBY_OPTS="--1.9 --server -Xcext.enabled=false -Xcompile.invokedynamic=false"