- Removed `--quiet` from the piprot check to see which packages are out
of date (check still works the same).
- Test on Python 3.5 and not 3.4 because Ansible is tested on 3.5 and
later.

- Replaced Debian Wheezy and Jessie Vagrant boxes.

didn't help.

This reverts commit e1804d8d.

# Conflicts:
#	.travis.yml

# Conflicts:
#	.travis.yml

- Try using Python 3.4 as it seems to be the oldest Python 3 version on which pre-commit tests (according to their Travis CI).

- Build on my supported platforms (some don't have properly working Vagrant boxes so they're allowed to fail).

- Enable free Ansible strategy to allow each host to proceed as fast as it can to help speed up some plays.

- Caching the entire virtualenv in Travis CI has proven to cause issues, caching just pip's cache directory.