Use an optimized grouped-by implementation over large sequences.
Clean up plugin usage.
- Exposed StackOverflowError potential for many individually added elements/tokens/activations to working memory.
- Swapped memory addition functions in clara.rules.memory (add-<elements|tokens|activations>! fns) `concat` calls with `into` to avoid stacking lazy seqs up to unknown bounds.
Merge pull request #59 from mrrodriguez/stack-overflow-large-mem-additions

Fix potential StackOverflowError when many elements/tokens/activations added to working memory
Merge branch 'master' into issue-16