More email package fixes.

MIMEApplication() requires a bytes object for its _data, so fix the tests.

We no longer need utils._identity() or utils._bdecode().  The former isn't
used anywhere AFAICT (where's "make test's" lint? <wink>) and the latter is a
kludge that is eliminated by base64.b64encode().

Current status: 5F/5E
4 files changed