Add `deface` as dependency

[benjaminwil]

What is the goal of this PR?

Because our test application includes solidus_auth_devise, which depends on deface, we didn't realize that we needed to explicitly depend on deface. We wrongly thought it would be available to all Solidus stores.

This commit should resolve issue #212.

How do you manually test these changes? (if applicable)

I would like to manually ensure the admin interface is working as intended to ensure we aren't creating problems for end users, like reported in this comment.

Merge Checklist

• [x] Run the manual tests
• [x] Update the changelog

[forkata]

Rebased to fix a conflict in the CHANGELOG