Add compression to values stored in Redis

[woop]

FeatureRows that are currently being stored in online stores like Redis are uncompressed. This helps to make debugging easier since the rows are somewhat human-readable using redis-cli.

However, in production it would be a lot more efficient to compress these values. We're able to achieve compression to around 40% of the original FeatureRow value at only 12 features. Larger feature rows would benefit even more from compression.

The proposal is to add support for compression as well as a flag to turn this on or off. We would also need to make sure that there is no performance hit during online retrieval.

[woop]

Duplicate of #515