fixing video thumbnail attributes so they have the correct number of quo...

...tes around them

See screenshot for malformed html - there's single quotes inside the double quotes for itemscope, itemtype, etc. 
![screen shot 2014-02-12 at 6 31 40 pm](https://f.cloud.github.com/assets/201367/2156277/02ba5748-9457-11e3-9a21-6765afb03424.png)

@kenkouot @saipetch