Fallback to not using turbolinks on error.

When there is an error fetching the replacement document the code should
try an old fashioned "full request".  This allows the browser to do
the things that the browser knows how to do in this situation including
hits to the applicationCache and error messaging.
added tests for offline/airplane mode
Merge pull request #158 from byliner/with_applicationCache_failover

With application cache failover