Allow headers paramter for ejsResource() to support authentication

[mcbain]

Current:
$scope.ejs = ejsResource(config.elasticsearch);

New (Example):
$scope.ejs = ejsResource({server: config.elasticsearch, headers: {'Access-Control-Request-Headers': 'accept, origin, authorization', 'Authorization': 'Basic ' + Base64Encode('user:Password')}});

Details http://stackoverflow.com/questions/19867663/how-and-where-to-implement-basic-authentication-in-kibana-3

[rashidkpc]

After quite a lot of testing, I've found that as long as the web server you're proxying elasticsearch with is properly configured for CORS there is no need to set the headers. I'd rather not hard code authorization to basic in any case