Travis builders are now on Ubuntu 11.04 "Natty". The xulrunner

package name is now "xulrunner-2.0". We need this to run our tests
in SpiderMonkey.

.travis.yml

@@ -1,5 +1,5 @@
 rvm:
   - 1.9.2
 before_script:
-  - sudo apt-get install xulrunner-1.9
+  - sudo apt-get install xulrunner-2.0
   - gem install rspec