Drop support for Python 2.7

[hugovk]

Python 2.7 reaches EOL on 2020-01-01 and many projects are dropping support for it.

Fixes #99.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• [n/a] Add tests for new features or tests that would have caught the bug that you're fixing.
• [n/a] Add new public functions/methods/classes to doc/api/index.rst.
• [n/a] Write detailed docstrings for all functions/methods.
• [n/a] If adding new functionality, add an example to the docstring, gallery, and/or tutorials.

TODO from #99:

• Edit the conda-forge recipe to build noarch since we no longer need different dependencies depending on Python version.

I'm not sure when to do this.

[welcome]

💖 Thanks for opening this pull request! 💖

Please make sure you read our contributing guidelines and abide by our code of conduct.

A few things to keep in mind:

• Remember to run make format to make sure your code follows our style guide.
• If you need help writing tests, take a look at the existing ones for inspiration. If you don't know where to start, let us know and we'll walk you through it.
• All new features should be documented. It helps to write the docstrings for your functions/classes before writing the code. This will help you think about your code design and results in better code.
• No matter what, we are really grateful that you put in the effort to do this! 🎉

[leouieda]

👋 @hugovk thank you for the contribution!

Edit the conda-forge recipe to build noarch since we no longer need different dependencies depending on Python version.

This would be done after the release only, so no need to worry about that now.

[leouieda]

Nice catch!

[leouieda]

This looks good to me! Made a few small wording changes. The CI failures are being caused by wrong sphinx versions in 3.5 builds. I'll try to fix that in #101 and then we can merge this 👍

[leouieda]

Alright! Nice to see all checks green 👍 I'll merge this in shortly. Just need to verify that we can drop 2.7 on master right now.

[welcome]

🎉🎉🎉 Congrats on merging your first pull request and welcome to the team! 🎉🎉🎉

Please open a new pull request to add yourself to the AUTHORS.md file. We hope that this was a good experience for you. Let us know if there is any way that the contributing process could be improved.

[leouieda]

@hugovk thank you for your contribution to Pooch! 🎊 🥂 We're always looking for feedback on the contributing process so any inputs would be very welcome. Feel free to add yourself to the AUTHORS.md file (if you wish).

[hugovk]

Thanks, added!

The contributing process was smooth, there was a clear checklist in the PR template, and plenty of extra info in the contributing guidelines. I only skim-read those as I was removing/refactoring, but looks like there's good info there for creating new features.

[leouieda]

Thanks for the feedback! And hope to have you involved in the future 🥇