Updated address length check to 1024 characters because many unsubscribe
links were much larger than our old limit (which was already 4x the RFC limit).
New limit is 16x the RFC limit.

Bumped the version of dnsq and expiringdict.

Moved mock and nose from install_requires to tests_require.
Make FallbackMimePart interface match with MimePart

To achieve that common functionality has been extracted to
 RichPartMixin that is mixed to both classes.
Merge pull request #49 from mailgun/maxim/develop

Make FallbackMimePart interface match with MimePart
Make FallbackHeaders interface match with MimeHeaders
Merge pull request #51 from mailgun/maxim/develop

Make FallbackHeaders interface match with MimeHeaders
Ignore false Content-Type headers

It is ignored in mesage/part bodies as well as in multipart
preambles and epilogues.
Fix a typo in the RichPartMixin name
Merge pull request #50 from mailgun/maxim/tokenizer

Ignore false Content-Type headers in multipart epilogues
Merge remote-tracking branch 'mailgun/master'

Conflicts:
	flanker/mime/message/fallback/part.py
	flanker/mime/message/part.py
	setup.py
	tests/mime/message/fallback/fallback_test.py