Epydemic

- Added extended Newman-Ziff algorithm for nested percolation
- Changed ther behaviour of NetworkExperiment to not delete the working
network in tearDown() at the end of a run, to simplify small-scale use,
but to replace it on setUp() instead
- Added a simple algebra of generating functions, including addition,
subtraction, and multiplication by constants and other generating
functions

- Added pulse-coupled oscillators
- Added core-periphery and modular ER network generators
- Added a cookbook recipe on defining network ensembles

- Refactored event rate distributions into Process instead of Dynamics
- Added per-edge infection variant of SIR
- Added a global random number generator to simplify replacement if needed
- Further documented event taps and dynamics
- Automated GitHub releases and Zenodo DOIs for each release
- Changed Makefilke target for doing a release to "release" (instead
of "upload"

- Added un-posting of posted events
- Changed StochasticDynamics to continue to run posted events even
after stochastic events become exhausted (rather than discarding
un-fired posted events). It remains the case that equilibrium overrides
posting
- Refactored event taps API to iunclude the process raising the event
- Added documentation cross-links to epydemic-signals as an example of
event taps
- Fixed times for execution of posted events
- Added test for removal of elements from loci when processing events
under synchronous dynamics

- Fixed another bug in SynchronousDynamics
- Added explanation of the two different Dynamics classes

- Fixed bug in process sequences under synchronous dynamics
- Refactored event rates calculations to not be per-process