Determine current feature support at the player level

[heff]

The volume and playbackRate controls currently hide themselves if the current tech (html5, flash, etc.) doesn't support the feature they need. In order to do this they currently have to access the tech directly to get this information, e.g. this.player_.tech.features ....

The goal of video.js is to abstract away the need to talk to the tech directly, so we need to find a better way to expose the current support for specific features.

It might look like this.player.features('volumeControl'). I'm not sure yet if that's the best way to phrase it or access that info.

You would use the loadstart event to check the current status of support and make updates as needed.

UPDATE

I'm currently like the player.supports() naming better, which was mentioned in #1474