Find/Create tool/functionality to simulate very slow BigTable reads & writes

[sming]

The main/only way that Heroic experiences BigTable strain is by greatly-slowed responses and time-outs.

We need to know how Heroic behaves when this occurs, lest Heroic's behavior make the situation even worse. Consider how (for example) unlimited retries + a query time-out that's too low would hammer BigTable (Heroic would endlessly repeat the same query).

Thus we need a tool to simulate BigTable struggling under load

[sming]

See this thread on Slack in #bigtable