Feature/refactor day2

[theFeu]

Main Topics:

• Remove Integrations Chapter on day2, time will be used for more CI
• Optimize CI Chapter and add new CI Labs
• Streamline Git Workflow Examples
• Optimize rebase and squashing Slides
• Reword a lot of slides to be clearer

Also:

Fixes #216

Fixes #200

[martialblog]

Hint: Needs to be rebased after day1 refactor is done, since I started this branch from the refactor-day1 branch