Tests now pass on ruby-head on all platforms.

.travis.yml

@@ -30,16 +30,13 @@ before_install:
 
 # Travis OS X support is pretty janky. These are some hacks to include tests
 # only on versions that actually work.
-# (last tested: 2016-10)
+# (last tested: 2016-11)
 matrix:
   # exclude: {}
   # include: {}
 
-  allow_failures:
-
-    # bundle fails on ruby 2.4 due to rdoc dependency on json
-    # https://github.com/flori/json/issues/303
-    - rvm: 'ruby-head'
+  # allow_failures:
+    # - rvm: 'ruby-head'
 
   # return results as soon as mandatory versions are done
   fast_finish: true