Add "printf" message

[diviak]

Would be nice to use something like this:

DBValidationStringLengthRule *stringLengthRule = [[DBValidationStringLengthRule alloc] initWithObject:_password keyPath:@"text" minStringLength:1 maxStringLength:50 failureMessage:@"Please provide password between %i %i"];
[_password addValidationRule:stringLengthRule];

Where you will replace min and max
Please provide password between %i %i"

Thanks