factor this out
add diag
introspection for if we're passing
pull this out too
actually, stop using tap4j

tap is simple enough that it doesn't buy us a whole lot, and java style
libraries are painful to work with because java is awful, and it doesn't
even provide a streaming interface, which is a pretty useful feature for
tap producers
include helpful messages for test failures
no, it's simpler this way
implement bail out
implement skip all