Use pdfminer3k to test body content.
Improve tag name for Docker image.
Add Dockerfile which builds a pdfminer3k .deb.
Rearrange Makefile.
Improve README.md.
Remove dependency used only for testing.
Add PDF content checking to test_FaultyAttachments.
Add PDF content checking to test_TestBasic.
Add PDF content checking to test_TestMIME.
Merge branch 'issue-44' - closes #44