CI sdist and manylinux1 support

[Korijn]

• Run linting on one platform to save some time
• Use auditwheel on Linux
• Build sdist on Linux
• Test installing wheels and sdists from temp folder so we can catch problems like in Installing from source dist does not work #38 in CI
• Include LICENSE file in built package
• Ensure binaries are not included in sdist
• Pin wheel==0.31.1, see Latest wheel==0.32.0 breaks auditwheel/wheeltools.py pypa/auditwheel#102
• Don't include the LICENSE file in the license kwarg, see Newlines in the description field produce a malformed PKG-INFO pypa/setuptools#1390
• For now, release step removes linux wheels just before uploading since they are not manylinux1 compliant

Closes #38