ROCSP: Compress OCSP responses for storage

[andygabby]

From some proof of concept tests, we could save ~30% on memory requirements for storing OCSP responses in Redis if we compress the responses using the compress/flate package.

[jcjones]

We'll want to prime a dictionary if we're doing this. To do that, we'd probably want to iterate through the prod and stage OCSP resposnes with a tool to find similar sections that we can hard-code.