Readme: We also support sha256 etc.

[sklemer1]

All Submissions:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you added an explanation of what problem you are trying to solve with this PR?
• 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?

[coveralls]

Coverage remained the same at 56.462% when pulling aac7c83 on sklemer1:patch-1 into 7dcc56d on IdentityPython:master.