Allow for initialising validator with localizedViolationString

[markst]

It would be nice if it were easier to update the localizedViolationString when initialising a violation object.

For example I currently have an extension on Validator which allows me to initialise with a violationString.

extension Validator {
    public init(violationString: String) {
        self.init()
        var condition = self.conditions.first!
        condition.localizedViolationString = violationString
        conditions = [condition]
    }
}

Which makes creating a form much easier when I have multiple strings per field:

self.controlForm.addField(passwordTextField, validator: PresentValidator(violationString: "Please enter your password"))

This is a good suggestion. Although it'd be preferred if this was an optional parameter with a default of nil so that way if none is passed in through the initializer, the default localized violation string is used. This way you don't need to have more than one init and continues to maintain API stability in the framework.

If you'd like to raise a PR for this enhancement, we'd love to review it!

[markst]

Sounds good. I'll PR once I get the chance