Support attribute placeholder variations

Hi @mikeerickson. For attribute placeholder, Laravel currently support 3 variations, which is :attribute, :ATTRIBUTE and :Attribute.

Fo reference: https://github.com/laravel/framework/blob/0c6f5f75bf0ba4d3307145c9d92ae022f60414be/src/Illuminate/Validation/Concerns/FormatsMessages.php#L289

It would be helpful if this library supports such feature as well. Below is the proposed patch that can provide the same feature:

_replacePlaceholders: function(rule, template, data) {
  var message, attribute;

  data.attribute = this._getAttributeName(rule.attribute);
  data.ATTRIBUTE = data.attribute.toLocaleUpperCase();
  data.Attribute = data.attribute.charAt(0).toLocaleUpperCase() + data.attribute.substring(1);
  data[rule.name] = data[rule.name] || rule.getParameters().join(',');

  if (typeof template === 'string' && typeof data === 'object') {
    message = template;

    for (attribute in data) {
      message = message.replace(new RegExp(':' + attribute, 'g'), data[attribute]);
    }
  }

  return message;
}

[mikeerickson]

I have completed implementation of this feature and will be part of the upcoming v3.5 release, which I am to release by the end of the week.

[apih]

I need it to support a custom language file as well. Currently, I am loading the custom language file using Validator.setMessages() method.