Update content.json

Embedded "What is a Browser" (youtube video) within "Navigation" and Gary Kovacs TED talk (youtube video) within "Privacy." Made small copy edit to "Privacy" blob to reflect this embed.
This should be an object, so instead of just a line of text, it needs to be identified as its content type.
```
{
  "type" : "markup",
  "content" : "Watch the video below. As you surf the Web, information is being collected about you. This <a href=\"http://www.ted.com/talks/gary_kovacs_tracking_the_trackers\">&ldquo;Tracking the Trackers&rdquo; TED Talk video</a> explains how."
},
```