GeezerVison

* fix typos, equation numbering in doc/flatsys.rst
* small updates (including numpydoc fixes) to statefbk.py, mateqn.py docstrings
* update setup.py contact info
* small fixes to iosys docstrings (from samlaf)
* update lqr() return type documentation (addresses python-control#418)
* added 2D array/matrix note to all functions using _ssmatrix
* PEP8 formatting updates for statefbk.py, mateqn.py (while I was at it)

* update lqe return values to match lqr
* update lqe docstring

…trol#478)

* updated markov() calculation + new unit tests
* updated markov() to add tranpose keyword + default warning; tests, PEP8
* resolves issue python-control#395

* fix footnote reference in markov() docstring

* require sphinx 3.4 or higher for readthedocs

Switch default state space matrix type to 'array' (instead of 'matrix')

…se-size

fix impulse size for discrete-time impulse response

skip impulse sampling for old scipy

and add unit tests

Extend returnScipySignalLTI() to discrete systems

Fix lqe docstring and input array type

…on-control#438)

* reorganize travis matrix, extend conftest.py

* pytestify bdalg_test

* pytestify canonical_test

* pytestify config_test

* pytestify convert_test.py

* pytestify ctrlutil_test

* pytestify delay_test.py

* pytestify discrete_test

* pytestify flatsys_test

* pytestify frd_test

* pytestify freqresp_test.py

* pytestify input_element_int_test

* pytestify iosys_test

* pytestify lti_test.py

* pytestify mateqn_test

* pytestify matlab tests

* pytestify minreal_test

* pytestify modelsimp

* pytestify nichols_test

* pytestify phaseplot_test

* pytestify rlocus_test.py

* pytestify robust tests

* pytestify sisotool_test.py

* pytestify slycot_convert_test.py

* pytestify statefbk tests

* pytestify statesp tests

* pytestify timeresp_test.py

* pytestify xferfcn_input_test.py

remove a lot of duplicate code by converting everything into
a single parametrized test function.

* pytestify xferfcn tests

* make tests work with pre python-control#431 source code state

revert this commit when merging a rebased python-control#431

(remove statesp_test.py::test_copy_constructor_nodt if not applicable)

* deprecate np.matrix usage

* print pytest summary for all except passing

Also make matarrayout and matarrayin function scoped fixtures so
that they can set the warnings filters individually as needed for
each test.

…" from python-control#438

This reverts commit 2b98769.

…re that combines systems with different timebases

…s default system timebase

…in parsing

…tems

…on-control#494)

* implementation of initial_phase, wrap_phase keywords for bode()

* add additional documentation on initial_phase if deg=False

* clear figure in unit tests to avoid slow plotting problem

TST: Error on Numpy matrix warnings

…ignals

I/O system improvements: linearize, interconnect, docstrings