ci: Run clippy for all targets
Benchmarks, tests, and so on are excluded by default.
Currently this has no effect on what code is checked, but it could
change things down the line.
ci: Enable test job
There are no tests right now, but this ensures that cargo-depgraph
compiles successfully on stable (there were no jobs using a stable
toolchain before), and will start running tests once they're added.
ci: Remove empty lines within job YAML
Enable and comply with some non-default lints
Update Cargo.lock for 1.6.0
Add `--depth` option
… and remove `--direct-dependencies-only`, as it is equivalent to `--depth 1`.
Add `--direct-dependencies-only` option
Add --include option
… and clean up a bit.
Add a note about graphviz to README.md