Ability to ignore case related errors.

I would like the ability to ignore errors regarding casing.

The problem is validating json with improper casing ie {Name:"Derek"} vs {name:"Derek"} generates the error "NoAdditionalPropertiesAllowed". This is the same as the error I would get with the validation against {name1:"Derek"}. What are the thoughts of adding a ValidationErrorKind.PropertyMismatch that makes it easier to distinguish this.

I'm happy to hope in and code this, just want to make sure its inline with the goals of this open source project first.

Thanks!