[README.md] Relative links repo files break when viewing in PyPi.org

[dancasey-ie]

Describe the bug
When viewing the README at (https://pypi.org/project/brightwind/) the relative links for LICENSE.txt and contributing.md break with Page Not Found.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'https://pypi.org/project/brightwind/'
2. Click on 'contributing.md'
3. Scroll down to '....'
4. See error

Expected behavior
The links should direct to the files in GitHub.

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context
Providing absolute links to the master branch is the probably the best approach, though when clicking links in the development branches they will be brought to the master github page rather than the relevant file in that branch.