create bash script to run foreman

- create bin/dev script to run both shakapacker and rails server in a single command
- make sure it reads from Procfile.dev which is the default file

bin/dev

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+if ! command -v foreman &> /dev/null
+then
+  echo "Installing foreman..."
+  gem install foreman
+fi
+
+foreman start -f Procfile.dev "$@"