Docs Improvements for Gitlab CI Integration

[coolprobn]

Current example for Gitlab CI Integration fails in CI due to following two reasons:

• cmake is required for rugged but it's not installed yet
• Gitlab CI fetches changes with git depth set to 20 by default and can't find the target branch

This PR is intended for improving the documentation so that configurations work as it is when copied to any gitlab-ci.yml

Changes Done:

• Install cmake required for rugged
• git fetch target branch for the PR
• Comments to elaborate some commands
• Link Blog "Integrate Pronto with Gitlab CI for Rails App" (Disclaimer, I am the Author)

These new changes can help beginners especially and can minimize issues like #457 and maybe this one too #441

[ashkulz]

Thanks for the contribution, @coolprobn!

[ashkulz]

0.11.3 has been released to RubyGems. Publishing future versions should be simpler due to implementation of Trusted Publishing workflow (c7007de) 😁