Minor fixups, tests

commit 1851efb95ce67cea88adf423ac00a80e3b78d9d8
Author: Daniel Farina <daniel@fdr.io>
Date:   Fri Dec 26 16:19:55 2014 -0800

    Add a tests that use the vault_digests feature
    
    Although added for convenience, it was never exercised in tests in
    c9ee3cd4ac0567a4e810ac377aac50bc1d0fe33c.

commit 5bebe1be2dba321256cabd27072e150797fb0fb9
Author: Daniel Farina <daniel@fdr.io>
Date:   Fri Dec 26 16:13:11 2014 -0800

    Fix bogus description: sha1 => hmac

commit 945ba732f3b94e301ccf4caa909e9ceb5a22b888
Author: Daniel Farina <daniel@fdr.io>
Date:   Fri Dec 26 16:11:44 2014 -0800

    Clean up whitespace and fix a linting error
    
    The "let (:key)" construct was the nearly-problematic one, because
    association rules allow (:key) to be a "grouped expression".