Combining multiple fixes

[ianfixes]

• Supercedes #4
• Supercedes #6
• Supercedes #8
• Supercedes https://github.com/mrako/wait-for/pull/5
• Supercedes https://github.com/mrako/wait-for/pull/8
• Fixes https://github.com/mrako/wait-for/issues/2
• Fixes https://github.com/mrako/wait-for/issues/3 including special handling for OSX
• Fixes https://github.com/mrako/wait-for/issues/4
• Fixes https://github.com/mrako/wait-for/issues/7

Overall, 2 tests have been added and the CI now runs them both inside and outside the docker container.

[victordidenko]

Took me a while to find out, why my application uses mysql port to bind... And this one is still not merged 😢