Switch from ZSETs to HASHes

[ckcr4lyf]

ZSET needs to waste resources to keys the keys (IP, port) organized in lexographical order. This is a waste for us, since for a tracker we don't need it to be sorted.

Additionally, we only needed a ZSET w/ score component so we can keep track of how old the elements are (via unix timestamp). However, Redis HASHes now have HEXPIRE on fields , which means they can be wiped automatically.

This also means we don't need a GC-style cleanup job on the DB.