.travis.yml in ffprober-0.3.3 vs .travis.yml in ffprober-0.3.4

@@ -6,5 +6,9 @@
   - 1.9.3
   - 2.0.0
   - jruby-19mode # JRuby in 1.9 mode
   - rbx-19mode
   - ruby-head
+
+matrix:
+  allow_failures:
+    - rvm: ruby-head