Reduce size of result from checkpoint.js #92
Description
We build up a rather large results object in checkpoint.js, this is then jsonified and sent to the python client which leads to some seriously large string building (enough that it has shown up in successive memory reports).
We can go back to our tricks of only specifying a value if unit and kind are defaults. We can not specify unit or kind if they're a default. We can omit values that are 0.
It's possible we could jsonify the results ourselves and then gzip them (I'm not 100% sure if that's exposed to JS) and then just send the blob back (although it would still probably have to be base64 plain text).
Yet another option would be to get the marionette folks to implement a test callback mechanism so we could batch results and reduce peak size at a cost of a gajillion messages.