transport.sendmail: Use subprocess instead of os.Popen
Added Travis-CI integration configuration.
Added note on marrow.interface dependency.
Prevent quopri-encoding the Date header.

The Date header was ending up like this:

    Date: =?utf-8?q?Sat=2C_01_Sep_2012_13=3A08=3A29_-0300?=

I was opening the received message in Thunderbird, using my
gmail account over IMAP and the date was not being read
correctly (not sure if this is Thunderbird's fault) and the
message would appear as if it were from 1969...

Anyway, the problem goes away if this header is pre-converted
to a bytestring. I don't think there is ever anything other
than ASCII in this header anyway.

Thoughts welcome...
Fixed typo in README
Fixed traceback with debugging logger
Merge pull request #50 from dsx/feature/dynamic-manager-fix

Fixed traceback with debugging logger
Merge pull request #49 from dsx/feature/readme-typos

Fixed typo in README
Merge pull request #46 from nandoflorestan/date_header

Prevent quopri-encoding the Date header.
Merge pull request #42 from plaes/transport-sendmail

transport.sendmail: Use subprocess instead of os.Popen
Base64 encode attachments
Set attachment filename independently of on-disk filename
Forgot to import base64 module
Merge https://github.com/jamiebegin/marrow.mailer into develop