remove default stage value in provider object

the current default is using AWS region naming syntax,
this mean other cloud provider would have to add extra code
to set their default value.

Instead, region default should be left to each provider.

lib/classes/Service.js

@@ -20,7 +20,6 @@ class Service {
     this.serviceObject = null;
     this.provider = {
       stage: 'dev',
-      region: 'us-east-1',
       variableSyntax: '\\${([ ~:a-zA-Z0-9._@\'",\\-\\/\\(\\)*]+?)}',
     };
     this.custom = {};