Publish checksum for Phar archive

I've finally ran into a use case for file checksums, besides verifying integrity:

If I want to make Saltstack manage my `wp-cli.phar` file for me, I need to give it a [source_hash](
http://docs.saltstack.com/ref/states/all/salt.states.file.html#salt.states.file.managed).

It would be trivial to publish an .md5 file next to the Phar archive.