Wrap each line of captions within its own <div>

[terrill]

Currently caption text is wrapped in this.$captionWrapper, which can include multiple lines of caption text. Wrapping each line in its own container would serve two purposes:

1. The inline-block for each line would only need to be as a wide as the text for that line (rather than one large block). This would result in less obstructive text when displayed as an overlay.
2. Will be one step closer to supporting roll-up captions (Add support for caption styles: pop-on vs roll-up #15) and WebVTT positioning (Add full support for WebVTT  #13)