Add table name to validation errors.

[andyday]

When validation (joi) errors occur there is no context to help determine what table the error occurred on. This small pull request fixes this. The more robust approach would be to extend Error and add table as a property and then modify the toString function, but that may be more than is needed.

[clarkie]

Would you like this ported to https://github.com/clarkie/dynogels

[andyday]

@clarkie sure. what's been added to this over vogels?

[clarkie]

Not a lot as yet but I'm working on it. I've updated joi bit still need to go to v9.

[clarkie]

Merged into dynogels. But now I'm confused as to what version to bump: http://stackoverflow.com/questions/38432774/semver-on-nested-object-in-javascript-major-minor-or-patch

[clarkie]

Released as part of Dynogels v5.0.2