adding wrapErrors options for wrapping errors into error class

[xpepermint]

Super simple solution for #51.

Example:

// ./validate.js

var validate = require('validate.js');
var ValidationError = require('../errors/validation_error');

validate.Promise = require('bluebird');
validate.options = validate.async.options = {
  fullMessages: false,
  wrapErrors: ValidationError
};

module.exports = validate;

// ./validation_error

module.exports = function ValidationError(params, message, options) {
  Error.captureStackTrace(this, this.constructor);
  this.name = this.constructor.name;
  this.params = params;
  this.message = message || 'Validation Error';
  this.options = options;
};

require('util').inherits(module.exports, Error);

// ./index.js

var validate = require('./validate');
var ValidationError = require('./validation_error');

var data = {
  name: ''
};
var contraints = {
  name: { presence: true, length: { minimum: 10 } }
};

validate.async(data, contraints).then(function() {
  console.log('ok');
}).catch(ValidationError, function(err) {
  console.log('ValidationError', err);
}).catch(function(err) {
  console.log('SystemError', err);
});

Run as

node index.js

[ansman]

I like this solution a lot! Super clean and maintains backwards compatibility.

I'll clean it up a bit and add some tests.

[xpepermint]

Cool, thx!