Fixes #51 - cache whether or not validation was successful when the ValidationResult object is created so that mutations to the underlying OperationOutcome do not change the validation result success status.
fixes a test which fails if the local time zone was not EST as the output from the formatter would change the offset of the reproduced string value.
Merge pull request #54 from jjathman/master

Fixes #51 - cache whether or not validation was successful when the Vali...