stringify key name if possible, closes #1552
Revert "stringify key name if possible, closes #1552"

This reverts commit 946c25e69ab85d9f0f50537a9bacc7ed0abee707.
coerce non-strings to null, test generateKey null and non-string returns
consolidate conditions
Merge pull request #1553 from spumko/1552/method_test

stringify key name if possible, closes #1552