Create a unique token in devtools/ to make it easier to count repos using cookiecutter-cms

[jchodera]

It would be useful to add some sort of unique token or phrase somewhere in devtools/ (where users are unlikely to extensively change or delete things) to better track deployments of cookiecutter-cms on GitHub.

[dgasmith]

You can search based off exact text in the README, example search here. At the same time adding a devtools/.tracking-token (and making everyone aware) with a line like molssi-cookiecutter-cms: version {full_git_hash} would allow much easier searching of over time versions.