allow_specifying_the_phoenix_port.diff

diff --git a/config/dev.exs b/config/dev.exs
index 06daee3..afb1189 100644
--- a/config/dev.exs
+++ b/config/dev.exs
@@ -7,7 +7,7 @@ use Mix.Config
 # watchers to your application. For example, we use it
 # with brunch.io to recompile .js and .css sources.
 config :blogpost_amnesia, BlogpostAmnesia.Endpoint,
-  http: [port: 4000],
+  http: [port: System.get_env("PORT") || 4000],
   debug_errors: true,
   code_reloader: true,
   check_origin: false,