feat: allow container re-use

[raddessi]

If the spawn and cleanup commands are skipped by overriding the fixture
commands to "", None, or False then existing containers can be left
around.

Having this as a native feature would be much cleaner than how I'm currently managing this. Thank you for all the work on this project, I've used it in many others with great success :)

[raddessi]

Ugh, I should have looked for PRs earlier, this is a dupe of #64

[Luminaar]

Hello,
Thank you for your contribution. I like your PR a bit more that the older one because with your change the command can be skipped entirely. I also appreciate that you updated the readme.

I have a couple of changes I would like to make but I'm unable to push them. I think I need permissions on your fork for that. Could you please grant me those?

[Luminaar]

Closes #63

[Luminaar]

Closes #54

[raddessi]

Sure thing! Im on mobile right now, ill update to allow edits today. Sorry, its been a busy few days i did not see this. Thank you!

[raddessi]

Huh I have this set to allow edits from you. What would you like changed?

[Luminaar]

I'm not able to push to your branch for some reason. Maybe I'm doing something wrong.
I've pushed my commits to this branch. If you agree with my changes and will incorporate those commits in the PR, I'll merge it and release a new version.

[raddessi]

Awesome! Im sure its fine, ill get it merged today for you. Thanks!

[Luminaar]

Ping, @raddessi

[raddessi]

Sorry, i see this every day i just havent got time for it. Busy week. I may today

[raddessi]

Nice! Looks good to me :) Thank you and sorry for the delay