Allow EMAIL_BACKEND to be set on new dictionary style settings
CommaSeparatedEmailField should handle single email address arguments.
New style settings only accept EMAIL_BACKEND
Fix wrong syntax
Updated migrations for to, cc and bcc fields.
Added Log.exception_type field.
Updated README.
Merge branch 'master' into new-style-settings

Conflicts:
	README.rst
Refactor how to determine post_office_backend
Merge pull request #67 from SeiryuZ/new-style-settings

Allow EMAIL_BACKEND to be set on new dictionary-styled settings
Updated README.rst
Moved parse_priority to utils.py.
recipients, cc and bcc fields now also accept single email addresses.
Slightly reshuffled docs.
DEFAULT_LOG_LEVEL -> LOG_LEVEL
Tweaked description in setup.py.
Minor cleanups.
Make Email.context field nullable.
Fallback implementation for Lockfile on Windows platform
Merge pull request #71 from wolfhechel/master

Fallback implementation for Lockfile on Windows platform