Added buttons and menu items to dismiss individual notifications (#76)

* Added DELETE verb for notifications

* Added notification dismiss button to status dropdown

* Added reveal-on-hover notif dismiss button, added FollowNotification component

config/routes.rb

@@ -175,7 +175,7 @@ Rails.application.routes.draw do
         end
       end
 
-      resources :notifications, only: [:index, :show] do
+      resources :notifications, only: [:index, :show, :destroy] do
         collection do
           post :clear
           post :dismiss