Warn if options / ready function are passed to a previously created player instance 

There are questions fairly regularly on Stack Overflow that come down to confusion over using both `data-setup` and passing options and/or a ready function to `videojs()`.

This change logs a message with `vjs.log` if options or a ready function are passed as arguments, if a previously created player is returned. It also adds note in the setup doc.
Here I think we can actually still use the player's ready function.
```
player.ready(ready);
```
The ready function [has a feature](https://github.com/videojs/video.js/blob/aeecca728e75da9977ffa9b9beea256642e8de3a/src/js/component.js#L771) where if ready as already fired, it will immediately execute the function passed to it.