Test for compatibility with unreleased versions of dependencies using GitHub Actions

[jpgill86]

Reproduce this automated test with GitHub Actions, which previously worked on Travis CI:

neurotic/.travis.yml

Lines 21 to 34 in 6f3c751

	- name: Future
	python: "3.9"
	before_script:
	# install dev versions of important packages
	- pip install -U \
	git+https://github.com/NeuralEnsemble/python-neo.git \
	git+https://github.com/NeuralEnsemble/ephyviewer.git
	# list versions
	- python --version
	- python -c "import os, sys; assert sys.version_info[:2] == tuple(map(int, os.environ['TRAVIS_PYTHON_VERSION'].split('.')))[:2]"
	- pip -V
	- pip list
	- conda list