fix: handle HEAD and PUT requests

[melanger]

do not ignore variables supplied using HEAD or PUT requests

see:

• https://www.rfc-editor.org/rfc/rfc2616#section-9.4
• https://www.rfc-editor.org/rfc/rfc2616#section-9.6

All Submissions:

• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Have you added an explanation of what problem you are trying to solve with this PR?
• [x] Have you added information on what your changes do and why you chose this as your solution?
• [ ] Have you written new tests for your changes?
• [ ] Does your submission pass tests?
• [ ] This project follows PEP8 style guide. Have you run your code against the 'flake8' linter?