Add temper feedback widget

![screenshot 2014-04-02 19 14 37](https://cloud.githubusercontent.com/assets/651753/2597938/9b14b066-babc-11e3-8727-27a71615d519.png)

Time to get some more feedback! This PR adds a Temper "was this article helpful?" widget to the following doc pages:

* embedding
* video seo
* export-settings
* customizing your video
* embed options
* wordpress

It also adds one specifically for the Wistia Basics video series page (see image).

These articles were chosen based on their traffic - they are the highest trafficked doc pages that are not for developers.

Just a temporary experiment, would be super easy to undo, but should get us some interesting data!

:calling: