Revert rapidjson merge
Merge #498 r=@kevinmehall: Revert rapidjson merge

Pulled the release due to regressions; might as well have master working while we figure out what to do.
(failing) tests for #473
give stack getter to *any* object on which Error.captureStackTrace is called, fixes #473
Merge #505 r=@tcr: Error.captureStackTrace now gives .stack to non-error objects

This fixes #473 and adds regression tests.
Merge branch 'master' into tcr-json
Merge branch 'tcr-json'