Add a circuit breaker to Content API client

![tumblr_inline_na61kozwk31raprkq](https://cloud.githubusercontent.com/assets/1001642/4073279/91357144-2e92-11e4-9cef-03079e475e0f.gif)

Have you checked how many failures happen for `article`? This is using blocking calls and would give a good indication on how sensitive this should be.