My preferred solution is Waxx https://www.waxx.io - It is Ruby and very fast. Mostly functions, no classes. Deploy like this:
waxx deploy stage or waxx deploy prod
The deploy script can be as simple as:
cd /path/to/folder && git pull && waxx migrate && waxx restart
Disclaimer: I am the author of Waxx and I wrote it to be as simple as possible yet still high performance and flexible.