Add :erts to extra_applications for 1.15 compatibility.

Author: jeremyjh

mix.exs

@@ -33,7 +33,7 @@ defmodule Dialyxir.Mixfile do
   end
 
   def application do
-    [mod: {Dialyxir, []}, extra_applications: [:dialyzer, :crypto, :mix, :syntax_tools]]
+    [mod: {Dialyxir, []}, extra_applications: [:dialyzer, :crypto, :mix, :erts, :syntax_tools]]
   end
 
   defp description do