Wheelhouse-uploader

- Fix support for PyPy tags:
https://github.com/ogrisel/wheelhouse-uploader/pull/37

- Make it possible to fetch sdist:
https://github.com/ogrisel/wheelhouse-uploader/pull/36

- Support absolute artifacts URLs.

- Pinning apache-liblcoud==2.2.1 dependency to workaround
2.3.0 installation problems under Windows.

- Upgrade dependency to latest apache-libcloud
- Use temporary files for upload and downloads to workaround
a bug with Python 3.7.

- Add explicit dependency on certifi to resolve SSL
verification issues on appveyor.
https://github.com/ogrisel/wheelhouse-uploader/issues/26

- Pin dependency apache-libcloud==1.1.0 to workaround
regression introduced by version 2.0.0:
https://github.com/ogrisel/wheelhouse-uploader/issues/22