logging errors in the console instead of the dom

[mziemer21]

This might close #13.

Instead of rendering errors to the dom it will log them to the console. This gives much better formatting, and now proptype warnings and error messages are in the same place.
Now:

Before:

[kylecesmat]

The reason we are showing errors in the DOM is so users interacting with the playground don't have to have the devTools open, and it allows people modifying the editor input to see errors quickly.

There might be incentive to show errors in the console (for stacktraces like mentioned in #13 ) but this approach is too limiting. Feel free to submit another PR that preserves the current behavior.