merge remote-tracking branch 'origin/master' into changes
[#51396943] add non-file attachement to send_mail

To attach non-file content (e.g. content not saved on disk), use
files_manually parameter and provide list of 3 element tuples, e.g.
[('design.png', img_data, 'image/png'),] which will be passed to
email.attach().
pep8 clean up in helper.py
Merge pull request #11 from Tivix/changes

Add non-file attachement to send_mail (without providing path to file)