Should be able to disable fullscreen button entirely

[alexrussell]

Either with a prop, or just the fact that switchToLandscape and/or switchToPortrait are not specified.

Also the isPortrait prop seems badly named for the prop that determines whether the "enter fullscreen" or "exit fullscreen" button should show. inFullscreen or something similar would make more sense. This would be especially true if #3 or #1 are ever done, as you could be viewing the video in landscape mode but not fullscreen.