Deprecate --commit-range

[consideRatio]

I want to deprecate this flag as is ignored currently by chartpress.py. I made it a soft deprecation where a warning is printed when --commit-range is used. I also removed the unused path_touched(*paths, commit_range) function.

$ chartpress --skip-build --commit-range test
Warning: use of --commit-range is deprecated.
$> git log -n 1 --pretty=format:%h -- .
$> git describe --tags --long e3d7223f
$> git log -n 1 --pretty=format:%h -- images/hub chartpress.yaml
$> git log -n 1 --pretty=format:%h -- images/network-tools chartpress.yaml
$> git log -n 1 --pretty=format:%h -- images/image-awaiter chartpress.yaml
$> git log -n 1 --pretty=format:%h -- images/singleuser-sample chartpress.yaml
Updating jupyterhub/values.yaml: hub.image: {'repository': 'jupyterhub/k8s-hub', 'tag': '0.9.0-alpha.1_2-e3d7223f'}
Updating jupyterhub/values.yaml: singleuser.networkTools.image: {'repository': 'jupyterhub/k8s-network-tools', 'tag': '0.9.0-alpha.1_0-320470f1'}
Updating jupyterhub/values.yaml: prePuller.hook.image: {'repository': 'jupyterhub/k8s-image-awaiter', 'tag': '0.9.0-alpha.1_0-320470f1'}
Updating jupyterhub/values.yaml: singleuser.image: {'repository': 'jupyterhub/k8s-singleuser-sample', 'tag': '0.9.0-alpha.1_0-320470f1'}

Closes #48

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Thank you @alzix for sharing the gist to deprecate an argparse argument!

❤️ 🌻