refactor components for easier testing

[bnchdrff]

we can use the container/component system, where a container makes all the bindings to state management (redux/react router) and then passes in clear, easily mockable functions to functional components.

i got lazy w/ many of the components and they are messy, currently.

see https://medium.com/@dan_abramov/smart-and-dumb-components-7ca2f9a7c7d0 and https://reacttraining.com/react-router/web/guides/testing for react-router specific stuff