max validator

var SomeModel = Backbone.Model.extend({
  validation: {
    age: {
	  max: 100
	}
  }
});

• number higher than max is invalid
• non numeric value is invalid
• number equal to max is valid
• number lower than max is valid
• numeric string values are treated as numbers
• when required is not specified undefined is invalid
• when required is not specified null is invalid
• when required:true undefined is invalid
• when required:true null is invalid
• when required:false null is valid
• when required:false undefined is valid