1.1.3dev: Remove compatibility with Python 2.1 (no email module) to 2.4 (old email module names).

Locals `email` imports were added in #386 for Python 2.1 compatibility.
Uppercase module names have been renamed according to PEP 8 standards since Python 2.5.
https://docs.python.org/2/library/email.html#package-history

git-svn-id: http://trac.edgewall.org/intertrac/log:/trunk@13577 af82e41b-90c4-0310-8c96-b1721e28e2e2