Fast-forward changes from upstream, enable testing

[Zeitsperre]

Overview

Changes:

• Merged with upstream master
• Cleaned up Makefile for a cleaner and more ordered help menu
• Adjusted tests to fit latest changes
• Small adjustments to docs
• Do not use test_requires for pytest-based projects
• Updated ReadTheDocs configuration
• Synchronized dependencies across top-level package and template
• Removed all references to Travis CI

Related Issue / Discussion

Additional Information

[cehbrecht]

@Zeitsperre we could remove travis-ci ... not used anymore ...

[Zeitsperre]

@cehbrecht

Will do! I wasn't sure if there were any projects in Bird-house that might still be using it.