Flying legend

[adamwiggins]

Transition animation causing legend to fly in from the left, let's remove.

Reproduce:

1. welcome notebook
2. comment out any of the plot lines

[brettimus]

Couldn't figure out how to disable, but this is the code that's the culprit:

https://github.com/masayuki0812/c3/blob/master/src/legend.js#L129

We don't have programmatic access to that option (withTransitionForTransform) at runtime, so any solution would have to dig into the internals of c3 pretty agressively