Packaging and other cleanup

[alanbriolat]

Overhaul and cleanup of project toolchain:

• Refactor project layout:
  • csbot/ to src/csbot/: prevent accidental test behaviour from current directory being in sys.path
  • csbot/test/ to tests/: better separation of tests from code, don't ship tests during packaging
• Preparation for packaging:
  • Move runtime dependencies to setup.py
• Better testing:
  • Use tox for testing multiple Python versions
  • Update Travis CI to use tox but also still use the build matrix
  • Move coveralls.io reporting into tox.ini, triggered if coveralls "factor" is in test environment name (e.g. py36-coveralls)
• Better docker:
  • Run as non-root user (UID and GID configurable with docker build --build-arg ...)
  • Speed up builds on Docker Hub by re-using built image for test phase
  • Make "build context" 100x smaller by using .dockerignore as a whitelist

[LordAro]

i thought we didn't want tests in the docker?

[alanbriolat]

Don't want tests in a Python package (e.g. bdist_wheel), but they are deliberately in the Docker image so that tests get run inside the image as part of the Docker Hub build process. That way we have confidence that the produced image will run the bot correctly.

(There may be better ways to run tests without leaving them in the image, but I couldn't figure out a better one yet.)