Rails 6 support in default deploy scripts

[mixflame]

I'm using git-deploy with Rails 6 and while I have workarounds for everything there are a few things left to be desired, and it's not fully automatic like it should be.

• asset:precompile task is now wrong, because rails has done away with app/assets

• For some reason, I have to regenerate my secret_key_base every time I deploy. I think this is my fault and I've taken steps to remove the credentials.yml.enc file from my repository, so we'll see if this goes away

Thanks @mislav !!! I use this stuff on everything!

[mislav]

Thanks for reporting! I don't use this myself much anymore, so this repo is basically archived, but if you want to send me a PR then I would gladly review it. 👍 ✨