refact: update project config

[sebthom]

This PR:

• removes obsolete travis config
• updates git config
• updates contribution guidelines and code of conduct
• bumps project version to 3.0.0-SNAPSHOT

[sebthom]

@vorburger these are the first 7 commits from #168 for easier reviewing.

[agentgt]

@sebthom and @vorburger still on vacation but will try to review changes and fix the website when I get back this coming Thursday.

Just didn’t want you to think I was ignoring the work.