Added remaining handlers to the External API

lib/koans/19_genservers.ex

@@ -18,14 +18,30 @@ defmodule GenServers do
       GenServer.call(__MODULE__, {:unlock, password})
     end
 
-    def change_password(old_password, new_password) do
-      GenServer.cast(__MODULE__, {:change_password, old_password, new_password})
-    end
-
     def owner_name do
       GenServer.call(__MODULE__, :get_owner_name)
     end
 
+    def manufacturer do
+      GenServer.call(__MODULE__, :get_manufacturer)
+    end
+
+    def laptop_type do
+      GenServer.call(__MODULE__, :get_type)
+    end
+
+    def retrieve_password do
+      GenServer.call(__MODULE__, :get_password)
+    end
+
+    def laptop_specs do
+      GenServer.call(__MODULE__, :get_specs)
+    end
+
+    def change_password(old_password, new_password) do
+      GenServer.cast(__MODULE__, {:change_password, old_password, new_password})
+    end
+
     ####
     # GenServer implementation