jsonschema should point at what part of the schema causes a SchemaError, similar to SyntaxError

[Julian]

This hopefully is a start to alleviate how hard it is to track down errors in large schemas, and shouldn't be too difficult to add.

[Julian]

Implementing this will be a good sanity check to make sure we have all of the structured information on our validation errors that will make this possible to implement.

I think actually that I'm going to take a stab at this tomorrow before going to release.

[Julian]

#90 starts on this.

We can iterate whenever we come up with other good ideas.