Frontend: Proper state management

[lwille]

With react, it's really difficult to react (no pun intended 😢) to state changes nicely. So far (see #26) I've been abusing the vowelList to pass a handler to the Editor component so the VowelPlotter can react to changes. I should at least use a proper EventEmitter pattern.

Micha and @dgrabla recommended these "state management" libraries for the problem:

• MobX
• Redux