Implement Independent Reducers

[shrugs]

fixes #15

• standardizes reducer construction / argument patterns
• removes the concept of a key from the reducer models, since that's actually just the purpose of the typestore itself
• allows reducers to be run in parallel
• caches api requests for 1 second in order to minimize issues with each reducer requesting the same block
• remove the global context for because operation and emit because now they're reducer-specific in ReducerContext
• those utilities are then passed into the reduction function
• abstract a reducer into, simply, ingest, output, and reduction function (store, abis, still pulled from global context)