anchor.diff:  create a key "success", "warning" or "error" in the flash class. Besides
   that, you can pass custom values to the flash class.
   
  -=== Flash in templates
  +==== Flash in templates
   
   To access the flash values, simply call the appropriate key in your
   template.
  
positive.code: index.ftl template and send the template along with a HTTP Status OK to
  the client.
  
  === Request and query parameter
  
  mangoo I/O makes it very easy to handle request or query parameter. Lets
  imagine you have the following mapping in your Routes class.
  
negative.code: The following classes can also be used directly in controller methods, but can not be used as a request or query parameter
  
  -------------------------------------------
  Request
  Session
  Form
  Flash
  Authentication
  Body
  -------------------------------------------
  
  === Request
  
  The request class is a special object which can be passed into a controller method. It enables you
  access to header and URL values a long with additional information about the request. To gain
  access to the request object, simply pass it to your controller method.
  
  [source,java]
  -------------------------------------------
  public Response index(Request request) {
      //Do something useful with the request
      return Response.withOk();
  }
  -------------------------------------------
  
  The request class is also useful when you have multiple query or request parameter which you don't want to
  name in your controller method header. To access a query or request parameter simply call the getter for
  the parameter.
  
  [source,java]
  -------------------------------------------
  public Response index(Request request) {
      String foo = request.getParameter("foo");
      return Response.withOk();
  }
  -------------------------------------------
  
  ==== Request parameter validation
  
  As an additional feature on the request object, you can validate incoming parameters. Just like
  <<Form handling>> you can access a Validator class, which can perform specific checks on the request
  parameter.
  
  [source,java]
  -------------------------------------------
  public Response index(Request request) {
    request.validation().email("foo");
    request.validation().required("bar");
  
    if (!request.validation().hasErrors()) {
       //Handle request
    } else {
       //Do nothing
    }
    ...
  }
  -------------------------------------------
  
  With this validation you can check an incoming request and return specific error messages, for e.g. as JSON.
  
  [source,java]
  -------------------------------------------
  public Response index(Request request) {
    request.validation().email("foo");
    request.validation().required("bar");
  
    if (!request.validation().hasErrors()) {
       //Handle request
    } else {
       return Response.withBadRequest()
          .andJSONBody(request.validation.getErrors());
    }
    ...
  }
  -------------------------------------------
  
  The error messages for the request use the same key as the form handling. Check
  the documentation on <<Form handling>> for more information on how to customize
  the specific error messages.
  
  === Form handling
  
  To access a form submitted to a controller class, you can simply pass
  the mangoo I/O Form class. Here is an example of how this might look
  