Add getElement and getElements

[abenoit]

Hello there,

Thanks for this binding library ! I've been using it to create behaviour tests in my ReasonML application.

I have been trying to snapshot test after simulating user's actions using enzyme. The snapshot method actually takes a ReasonReact.reactElement. When I tried to use getNode a warning said that the method was deprecated and that we should rather use getElement. Enzyme changelog is here https://github.com/airbnb/enzyme/blob/master/CHANGELOG.md#documentation-2

I've added the two missing methods in the bindings (I intentionally left the deprecated getNode and getNodes methods for people to get the warning message)

[rhysforyou]

Thanks for this! I'll push out a new release shortly.

[rhysforyou]

Alright, I've published this as v0.6.0

[abenoit]

Yay cool ! Thanks a lot 👍 🎉