Show error message for older browsers lacking flash

We currently aren't showing the message to tell a user they need to install flash for the non-html5 video fallabck to work correctly.

![littlesnapper](https://cloud.githubusercontent.com/assets/80089/3840956/45821e50-1e25-11e4-9c88-39ef8a769031.png)

/cc @rich-nguyen @gklopper