test the `peru file` field
test the `peru file` field

Summary:
Normally peru looks at the path `./peru.yaml` in a module to figure out
whether that module is itself a peru project. The `peru file` field lets
users customize that path. This diff adds a test for that behavior.

Reviewers: sean

Differential Revision: https://phabricator.buildinspace.com/D178

olson-sean-k/peru,nivertech/peru,enzochiau/peru,buildinspace/peru,ierceg/peru,scalp42/peru,ierceg/peru,olson-sean-k/peru,oconnor663/peru,buildinspace/peru,oconnor663/peru,enzochiau/peru,nivertech/peru,scalp42/peru