Upstream changes

[Zeitsperre]

Overview

This PR fixes #99

Changes:

• Integrated changes from upstream master, including re-enabling tox
• Restored removed documentation

Related Issue / Discussion

Re-enabling tox is particularly high in the priorities list, given the changes that have come to pass with Travis CI. At the very least, we now know the risks associated with tying ourselves to a specific service API.

There are quite a lot of changes in here. Even though I performed a rebase-type merge to gradually solve the merge conflicts (time-consuming), there is likely a lot here to unpack. Some of my goals were as follows:

• Make pytest optional (selecting against it removes much of the pytest-based code we have).
• Make Click optional to benefit from upstream changes that use argparse instead.
• Leverage tox where possible and have CI services rely more on makefile recipes.
• Restore most of the documentation that was previously removed so users/developers know how to contribute here.

Additional Information

https://github.com/bird-house/cookiecutter-birdhouse/issues/99 https://github.com/Ouranosinc/xclim/issues/509

[tlvu]

This is a large PR. Will be a few days before I can have time to digest it. Hope it's okay.

[Zeitsperre]

@tlvu It still isn't working, so no rush. The merge process took a few hours and still needs a cleanup.

[Zeitsperre]

Closed. Was able to get this working with #110