Stochastic-matching

As the package is at early stage, it had to go through a lot of refactoring.
Hopefully, the result should be more easy to use.

Major changes:

* API completely unified
* Beginners (and intermediate) users should always go through the Model class to use the package.
* Advanced users: the documentation reference is your oyster!
* New features
* A few new graph models.
* New analysis tools: left kernel, right kernel basis change and display (for simple graphs),
injectivity/surjectivity, connected components, spanners, and vertices!
* New policies for the simulator: *priority* and *semi-greedy*!

Minor changes:

* Default rates are proportional to degree (but you can ask for 'uniform')
* We have a logo!
* Hunt for typos in documentation.
* Notebooks tutorials have been updated to cope with the new API.

* First release on PyPI.
* Refactoring: the package name for the public release is *Stochastic Matching*.
* The graph submodule has been revamped a bit:
* Obtaining graphs by concatenation of other graphs is now more systematic and optimized.
* Names of generators have been changes to comply with *official* terminology from Wolfram.
* A few more generators have been added (e.g. complete, lollipop, barbell).
* Current compatibility: 3.6 -> 3.9

* Add possibility to specify node names. The names are used for all display operations
* New simulator method compute_ccdf to allow access outside show_ccdf
* Simulator method show_ccdf has two new options: indices (only show some nodes), sort
* New simulator method compute_average_queues
* New simulator method show_average_queues with three options: indices (only show some nodes), sort,
and as_time (divide by arrival rates)
* New *Getting started* notebook.
* Doctests parameters adjusted for faster test suite execution

This update reintroduces simulators, fully revamped

* All simulators are built as a hierarchy of classes
* Simulator is the mother abstract class
* QueueSizeSimulator is dedicated to greedy simulators that only use the queue sizes:
RandomNode, RandomItem, and LongestQueue.
* QueueStateSimulator is dedicated to greedy simulators that use the age of items:
FCFM.
* VQSimulator is a fast implementation of the virtual queue algorithm.
* All non-abstract simulators have a string name. The new `get_simulator_classes()`
gives a dict of them that can be used to easily select a given simulator.
* Lots of refactoring
* nodes and edges attributes from graph renamed as incidence and co_incidence respectively.
Older incidence attribute (plain matrix) removed.
* spectral.py moved up to main module
* New simulator module
* simulator.py split into classes.py and a few other files inside the simulator module.
* Jit is disabled for the testing (allows for inner coverage inspection).
* Tutorials revamped to cope with 0.0.3.
* Old files removed from git for cleanliness

Lots of changes in this update.

* Graph API has been fully revamped. There is now a GenericGraph class from which SimpleGraph and HyperGraph are derived.
* Hypergraphs don't have any adjacency attribute, only incidence. They are displayed as bipartite graphs between
nodes and edges, with an option to explicitly separate nodes from edges.
* Simple graphs are mostly similar but not compatible with previous Graph class.
* Hovering on edge now show edge id and description, e.g. edge 6 between nodes 1 and 4 will show "6: (1, 4)"
* TWO HYPERGRAPHS GENERATORS have been added to the mix:
* hyper_dumbbells can create the candy and larger sweets with trivial kernel.
* fan can create hypergraphs with more complex kernels, possibly with bipartite-like degenerescence
* The old gramian module is now called spectral.
* All internals have switched from gramian-based computation to incidence-based computation,
which makes it fully hypergraph ready (multiplicity / loops should work, but are not tested yet).
* NEW MAXIMIN FLOW COMPUTATION! No need to optimize each edge, one single linear optimization is enough and
the result maximizes the minimal edge flow.
* is_stable method checks the graph kernel dimension and existence of a positive solution.
* Main class as been revamped as well
* Class name is now MQ (could be changed later).
* When displayed, flows are checked by default. Conservation law issues gives red nodes, negative edges are red,
null edges are orange (can be disabled).
* SIMULATION ENGINE NOT AVAILABLE IN 0.0.2, as there are a lot of things to change. It will return in 0.0.3.
* Misc:
* Tutorials (simulation apart) have been updated. Enjoy the double degenerated fan!
* Local coverage computation. Enforcing 100% coverage on all 0.0.2+ code.
* Minor changes in the display module to cope with the new graph API.