Minimum Ruby version is 2.4

[lzap]

• Drop older and unsupported Ruby versions up to 2.3.x.
• Remove committed .ruby-version file and add it to gitignore
• Update Rubocop configuration so modern Rubocop can actually work

[plribeiro3000]

@lzap You are doing several structural refactorings over here. Could you split them in different PR's or at least in different commits?

I have some concerns about your changes:

• Update rubocop just for the sake of update and add everything as something safe to be fixed later is not a good approach as those are gonna get forgotten
• We need to be sure about the version dependency as fog still support 2.0.0+ because of some constraints we have with old linux distros in LTS
• I personally do like .ruby-version and .ruby-gemset to be in the project so i don't have to worry about it every time i have to pull the project again

Can we split all of those and talk about them separately?

[lzap]

It's fine, was just a suggestion, looks like you don't like it all so I will just close it.