Sequence

Added
- quantum state manager for quantum memories
- quantum circuit class (for use with quantum memories)
- `qutip` library dependency

Changed
- rewrite of quantum entanglement class
- change all optical channels to one-way

Added
- logging functionality with `log` module
- cached quantum state measurement

Changed
- changed all quantum state representations from list to tuple
- event removal system
- example scripts now use `Timeline.seed()` method
- `Timeline` event removal method

Added
- observer functionality for entities
- README file for documentation

Changed
- some method-level docstrings
- convert all component constructors from keyword to positional arguments
- change documentation directory from `sphinx` to `docs`

Removed
- push/pop functions for entities and non-stack protocols
- some unnecessary entity attributes