Bugfixes: Attachment extension; UTF16 characters in body
Added testcases for bugfixes
Moving e-mail examples alongside other e-mail messages.
Reorganizing tests.
Revamping encoding handling to normalize encodings to UTF-8 for storage; back into original encoding during rehydration.
Set email payload's charset after all other headers.
Cleaning up tests; moving test e-mail messages; fixing bugs relating to message encoding rehydration.

--HG--
rename : django_mailbox/tests/generic_message.eml => django_mailbox/tests/messages/generic_message.eml
rename : django_mailbox/tests/message_with_attachment.eml => django_mailbox/tests/messages/message_with_attachment.eml
rename : django_mailbox/tests/message_with_defective_attachment_association.eml => django_mailbox/tests/messages/message_with_defective_attachment_association.eml
rename : django_mailbox/tests/message_with_defective_attachment_association_result.eml => django_mailbox/tests/messages/message_with_defective_attachment_association_result.eml
rename : django_mailbox/tests/message_with_image_jpg_mimetype.eml => django_mailbox/tests/messages/message_with_image_jpg_mimetype.eml
rename : django_mailbox/tests/message_with_long_text_lines.eml => django_mailbox/tests/messages/message_with_long_text_lines.eml
rename : django_mailbox/tests/message_with_many_multiparts.eml => django_mailbox/tests/messages/message_with_many_multiparts.eml
rename : django_mailbox/tests/message_with_many_multiparts_stripped_html.eml => django_mailbox/tests/messages/message_with_many_multiparts_stripped_html.eml
rename : django_mailbox/tests/message_with_utf8_char.eml => django_mailbox/tests/messages/message_with_utf8_char.eml
rename : django_mailbox/tests/multipart_text.eml => django_mailbox/tests/messages/multipart_text.eml
Adding tests and minor code changes to ensure that we properly handle the distinction between bytes and text when dehydrating/rehydrating messages.
Remove unicode literals from tests for Python3.
Base64-encode message body when storing in DB.

* Since Django requires that the content stored in a TextField be unicode, we
  need some way to encode the message safely.  In situations before where
  a single-byte non-7-bit-clean encoding were used, django-mailbox could
  explode when writing the message copy to the database; this should ameliorate
  that problem.
* Reverts earlier changesets' encoding normalization.
Removing leftover logger.
Bumping major revision number given new migration and changes to DB storage of message body.
Added tag 3.0 for changeset ca5dcd16990a