Dropped support for Python 2

[claudep]

No description provided.

[coveralls]

Coverage increased (+0.7%) to 90.061% when pulling 1633cc3 on claudep:droppy2 into 0badc75 on emcconville:master.

[claudep]

Note I didn't touch changelog.rst yet.

[emcconville]

Hey thanks for this body of work! I originally started thinking about dropping Python-2 for Wand-0.6.x, but got a lot of push back from legacy users. I think the current Python-2 users make up about 20% of Wand downloads.

[claudep]

Sure, you choose when the best moment is to drop Python 2. I took the risk to prepare the patch without asking first, so don't feel any pressure to push it now.
Once done, legacy users can still use wand as long as they pin it in their requirements (e.g. wand < 0.7.x).

[emcconville]

Sounds good to me!