Bumps the minimum dimod version to a modern version
Use dwave-samplers rather than dwave-greedy
Make the versions in requirements.txt match the oldest supported for each package
Test with the minimum version and latest in CI
Drop NetworkX from tests/requirements.txt in favour of letting dwave-networkx set the version. This makes our CI a bit simpler at the expense of a bit of explicitness.
This commit does a few things: