Feature development:
* Added powerful new reinforcement learning decision module: Perturbative Q-Learning (27).
* Added array-based decision-mutable values as well as variable constraint types (23):
* Boolean Array, no constraints.
* Integer Array, range constraint.
* Float Array, range and sum constraints.
* New Tutorial! (16)
* New Economic trader simulation. see examples/comparative_advantage (17).
Bugfixes: 12, 19, 21