Once initialized, Drizzle instantiates web3 and our desired contracts, then observes the chain by subscribing to new block headers.
Drizzle keeps track of contract calls so it knows what to synchronize.
When a new block header comes in, Drizzle checks that the block isn't pending, then goes through the transactions looking to see if any of them touched our contracts.
If they did, we replay the calls already in the store to refresh any potentially altered data. If they didn't we continue with the store data.
