Remove versioneer section

[cabb99]

I have noticed that the DevTools README (lines 47–56) still refers to Versioneer.

cookiecutter-cms/{{cookiecutter.repo_name}}/devtools/README.md

Lines 47 to 56 in 6180f9c

	## Versioneer Auto-version
	[Versioneer](https://github.com/warner/python-versioneer) will automatically infer what version
	is installed by looking at the `git` tags and how many commits ahead this version is. The format follows
	[PEP 440](https://www.python.org/dev/peps/pep-0440/) and has the regular expression of:
	```regexp
	\d+.\d+.\d+(?\+\d+-[a-z0-9]+)
	```
	If the version of this commit is the same as a `git` tag, the installed version is the same as the tag,
	e.g. `{{cookiecutter.repo_name}}-0.1.2`, otherwise it will be appended with `+X` where `X` is the number of commits
	ahead from the last tag, and then `-YYYYYY` where the `Y`'s are replaced with the `git` commit hash.

Since this cookiecutter template now employs versioningit for version management, I think that reference should be updated.