Remove deprecated lifecycle hooks, context, and pure

[ryanbrainard]

Builds upon #217 to fix #217 and #231.

This moves from the deprecated componentWillMount and componentWillReceiveProps to componentDidMount and componentDidUpdate. To also moves away from the deprecated context. To support this, the pure option is also removed to avoid infinite loops in the setting state.

Unit tests have been updated and a light exploratory testing have been done on a real app, but more of the latter likely needs to be done. I have cut 3.0.0-0 beta for this if anyone wants to take it for a spin.

[spicysouvlaki]

This looks good for a beta. I'd like to see us try it out for a little while before a 3.0.1. We probably also need to come back and update the README and other docs at that point too.