Complex assetions like deepEquals and satisfies plugins should differentiate between bail outs and internal errors

[pygy]

Currently, if a crash happens in the deepEquals code (as in #41), or in a .satisfies plugin, this is reported as a bailout.

Crashes in user code (e.g. an getter that throws when doing a deepEquals, or some other failure in user code called from the satisfies() validator) should cause bailouts, but errors in ospec and validators should throw errors and exit ASAP with a corresponding stack trace.