feat(RouterStore): Use observable references

Instead of converting the store attributes to observable objects just use observable references as
their values are always mutated

BREAKING CHANGE: The store attributes are not @observable anymore but @observable.ref

src/modules/RouterStore.js

@@ -3,13 +3,13 @@ import transitionPath from 'router5-transition-path';
 
 class RouterStore {
 
-  @observable route = null;
-  @observable previousRoute = null;
-  @observable transitionRoute = null;
-  @observable transitionError = null;
-  @observable intersectionNode = '';
-  @observable toActivate = [];
-  @observable toDeactivate = [];
+  @observable.ref route = null;
+  @observable.ref previousRoute = null;
+  @observable.ref transitionRoute = null;
+  @observable.ref transitionError = null;
+  @observable.ref intersectionNode = '';
+  @observable.ref toActivate = [];
+  @observable.ref toDeactivate = [];
   // @observable currentView;
 
   router = null;