Add shebang line to post_deploy shell script

Procfile

@@ -1,4 +1,3 @@
-worker:          bundle exec rake jobs:work
-rabbit_workers:  bin/rails r lib/rabbit_workers.rb
-web:             bundle exec passenger start -p $PORT -e $RAILS_ENV --max-pool-size 2
-release:         bundle exec rake api:build_assets
+worker:         bundle exec rake jobs:work
+rabbit_workers: bin/rails r lib/rabbit_workers.rb
+web:            bundle exec passenger start -p $PORT -e $RAILS_ENV --max-pool-size 2

bin/post_compile

@@ -1 +1,3 @@
+#!/bin/sh
+
 bundle exec rake api:build_assets