Build standalone binary wheels for Linux and Mac OS

Based on http://github.com/ligo-cbc/minlal, but with a few improvements:

• Build for all supported Python ABI versions
• Put common dependencies inside Docker image to speed up builds
• Tidy and integate with LALSuite's CI setup
• Use the auditwheel tool for shared library cleanup on linux

Note that this should probably be triggered by top-level release tags, e.g.:

only:
  - /^lalsuite-v/

The packages should be usable but larger than necessary due to a bug that I reported in auditwheel.