mail/py-dkimpy: update 0.5.4 -> 0.5.6

Changes:
2015-12-07 Verion 0.5.6

• Brown paper bag release, 0.5.5 tarball inadvertently included pyc files and other artifacts from development

2015-12-07 Version 0.5.5

• Fix and test case for case insensitive subdomain matching.
• Python3 compatibility fixes and test cases thanks to Diane Trout

PR: 205128
Submitted by: Kevin Golding <ports@caomhin.org> (maintainer)