Add Custom Messages for Sails

Supports the following syntax for Waterline Models.

`{data}` is replaced with the offending value
`{rule}` is replaced with the value the validator is checking against

````
  attributes: {
    email: {
      type: 'string',
      email: { value: true, message: 'woah homie that\'s not an email {data}  {rule}' },
      minLength: { value: 10, message: 'not long enough, it should be at least {rule} big' },
      maxLength: { value: 12, message: 'woah there cowboy, that\'s {rule} too big' }
    }
  }
````