Print out nice message when not loaded

It turns out to be pretty easy to run `VintageNet.info` before
`VintageNet` is loaded if you're impatient. I do this regularly. This
makes it print a nice message rather than raising an exception in
`elem/2`.

lib/vintage_net/info.ex

@@ -6,11 +6,19 @@ defmodule VintageNet.Info do
   """
   @spec info([VintageNet.info_options()]) :: :ok
   def info(opts \\ []) do
-    version = :application.loaded_applications() |> List.keyfind(:vintage_net, 0) |> elem(2)
+    case version() do
+      :not_loaded ->
+        IO.puts("VintageNet hasn't been loaded yet. Try again soon")
 
-    IO.write("""
-    VintageNet #{version}
+      version ->
+        IO.puts(["VintageNet ", version])
+
+        do_info(opts)
+    end
+  end
 
+  defp do_info(opts) do
+    IO.write("""
     All interfaces:       #{inspect(VintageNet.all_interfaces())}
     Available interfaces: #{inspect(VintageNet.get(["available_interfaces"]))}
     """)
@@ -32,6 +40,15 @@ defmodule VintageNet.Info do
     end
   end
 
+  defp version() do
+    Application.loaded_applications()
+    |> List.keyfind(:vintage_net, 0)
+    |> case do
+      {:vintage_net, _description, version} -> version
+      _ -> :not_loaded
+    end
+  end
+
   defp print_config(ifname, prefix, opts) do
     configuration = VintageNet.get_configuration(ifname)