rangeLength validator

var SomeModel = Backbone.Model.extend({
  validation: {
    password: {
	  rangeLength: [6, 100]
	}
  }
});

• string with length equal to last value is valid
• string with length equal to first value is valid
• string with length shorter than first value is invalid
• string with length longer than last value is invalid
• string with length within range is valid
• when required is not specified null is invalid
• when required is not specified undefined is invalid
• when required:false undefined is valid
• when required:false null is valid
• when required:true undefined is invalid
• when required:true null is invalid