Make validation error levels configurable / customizable

[Marak]

Currently, resourceful handles the construction of validation errors somewhat manually. The validation itself is performed in revalidator, with the results being passed to resourceful.

The issue is that resourceful has a bunch of lines like : var e = { validate: validate, value: obj, schema: this.schema };

This manual construction of e should all be replaced with a common function for constructing validation errors. This function should be able to be configurable / swappable. The goal is to be able to easily change the level of details that a validation errors return.

The errs library could be used inside this common construction function.

[Marak]

invalid

[Charlie Robbins]

Duplicate of #146