Merge branch 'master', remote-tracking branch 'origin'
Skip webp mux with the right skip message
Merge pull request #954 from wiredfool/webp-test-comments

Webp Metadata Skip Test comments
Update CHANGES.rst [CI skip]
Allow latest PyPy 2.4.0 to fail and temporarily add previous passing 2.3.1 for the time-being (#952)
Fix allow_failures
Merge pull request #956 from hugovk/pypy-regression

Workaround Pypy regression