Rename dummyCollector to noOpCollector
Fix error messages in in-mem dictionaries
Register request and responses for gob
Adds tests for layered transactional state
Adds minScore as a parameter to optimizer
Fix broken stat test cases
Batch messages in each transaction

This commit enables bees to batch messages for each transaction. This
improves the throughput of bees by 3 orders of magnitude.
Optimize transactions

This commit adds a few micro-optimizations for transactional
dictionaries. It lowers the overhead of a transaction about
50% on average.
Add comments for ErrInvalidCmd
Add microoptimizations in channels

This commit has a performance gain of +5%.