Add Theme Picker.

Moved Provider into App.js. Add AppContainer to store theme in redux
store. Add reducers and actions for theme, SET_THEME.

reducers/index.js

@@ -3,11 +3,13 @@ import { combineReducers } from "redux";
 import timetable from "./timetable";
 import classes from "./classes";
 import subjects from "./subjects";
+import theme from "./theme";
 
 const rootReducer = combineReducers({
 	timetable,
 	classes,
 	subjects,
+	theme,
 });
 
 export default rootReducer;

reducers/theme.js

@@ -0,0 +1,9 @@
+import themes from "../themes";
+export default function theme(state, action) {
+	if (typeof state === "undefined")
+		return themes[0].theme;
+	if (action.type === "SET_THEME") {
+		return action.theme;
+	}
+	return state;
+}