Allow failure of ~> 3.2.17 for the moment.

This is because the security release of `3.2.22.1` was not correctly
tested against 1.8.7 which means that our build will not pass against
this ruby. /cc @pixeltrix.

Author: Sam Phippen

.travis.yml

@@ -88,6 +88,15 @@ matrix:
     # MRI 2.2 is not supported on a few versions
     - rvm: 2.2
       env: RAILS_VERSION='~> 3.1.12'
+    - rvm: 2.3.0
+      env: RAILS_VERSION='~> 3.1.12'
+  allow_failures:
+    - rvm: 1.8.7
+      env: RAILS_VERSION='~> 3.2.17'
+    - rvm: 2.2.2
+      env: RAILS_VERSION=master
+    - rvm: 2.3.0
+      env: RAILS_VERSION=master
   fast_finish: true
 
 branches: