Add --skip-tests Flag

[mjhasbach]

I had to deprecate one of my packages today. The tests are failing, preventing release-script from releasing. As a workaround, I am just going to remove scripts.test from my package.json, but it would be cool if there was a flag to skip tests.

[AlexKVal]

@mjhasbach https://github.com/AlexKVal/release-script/releases/tag/v0.5.6 has been released ❇️ 😉
🍒

[mjhasbach]

Thanks!