Merge branch 'master' into community-master

[tagliala]

• Test against latest ruby versions
• Set Ruby version to 2.5.1
• Drop Ruby 2.2 compatibility
• Use RuboCop RSpec
• Move development gems in a group

Yes, I know. This is a hell of commit but as I mentioned before I did a lot of work on this gem since the last year

Also, I've removed the aggregated failures because RuboCop RSpec sees them as a single spec containing a lot of lines.

[Ch4s3]

Looks good. We’ll figure it out if there are issues.