RedisCacheAdapter: add some additional checks and defaults

[TylerBrock]

This PR cleans up the comments a bit and makes the TTL for RedisCacheAdapter saner. It behaves like this:

• If the ttl is not provided -> set key using DEFAULT_REDIS_TTL
• If the ttl is provided and less than zero or NaN -> set key using DEFAULT_REDIS_TTL
• If the ttl is provided and 0 -> do nothing
• If the ttl is provided and Infinity -> set key permanently
• If the ttl is provided, positive, and non-zero -> set key with provided ttl in milliseconds

[flovilmart]

@TylerBrock maybe remove dump.rdb from the commit :)

[TylerBrock]

DOH, thx

[facebook-github-bot]

@TylerBrock updated the pull request - view changes

[flovilmart]

LGTM! Merge when you feel :)