added ajax controller thing

app/controllers/ajax/friend_controller.rb

@@ -1,11 +1,37 @@
 class Ajax::FriendController < ApplicationController
   def create
+    params.require :screen_name
+
+    target_user = User.find_by_screen_name(params[:screen_name])
+
+    begin
+      current_user.follow target_user
+    rescue
+      @status = :fail
+      @message = "You are already following that user."
+      @success = false
+      return
+    end
+
     @status = :okay
     @message = "Successfully followed user."
     @success = true
   end
 
   def destroy
+    params.require :screen_name
+
+    target_user = User.find_by_screen_name(params[:screen_name])
+
+    begin
+      current_user.unfollow target_user
+    rescue
+      @status = :fail
+      @message = "You are not following that user."
+      @success = false
+      return
+    end
+
     @status = :okay
     @message = "Successfully unfollowed user."
     @success = true