Handle live broadcasts (Youtube/Facebook)

[vheuken]

This has been discussed in #151 with @Brotakuu

• .live_stream? function that returns whether or not the video is a live broadcast
• .live_status function that returns a symbol reflecting the status or nil if it is not a live stream. Potential return values are :live, :upcoming, and :ended, though we should look into the info we can get from Facebook and Youtube first.
• Need to figure out how to test, since a broadcast can't be live or upcoming forever.

[Brotakuu]

Looks like facebook similarly has a live_status field that returns enum status of the video.

https://developers.facebook.com/docs/graph-api/reference/video/

[vheuken]

Right. We'd need to find out exactly what it returns. I'll try to play with it tonight while I'm working on FB support.