[3.4] Backport CI config from master (#2475)

[3.4] Backport CI config from master (#2475)

* Issues #23808, #25911: Trying to fix walk tests on Windows.

On Windows a symlink can has the FILE_ATTRIBUTE_DIRECTORY flag.

(cherry picked from commit 388b90f28e029daaf06aae8026b596e2f20a1cd3)

* bpo-30231: Remove skipped test_imaplib tests (#1419) (#2193)

The public cyrus.andrew.cmu.edu IMAP server (port 993) doesn't accept
TLS connection using our self-signed x509 certificate. Remove the two
tests which are already skipped.
(cherry picked from commit 7895a0585b4b6a1c8082d17227307c6ce2c8bb8b)

* Backport CI config from master

* Add .travis.yml for Travis CI
* Add .github/ for AppVeyor and CodeCov.

* Travis CI: remove "make regen-all" check

The regen-all Makefile rule doesn't exist in Python 3.4, only since
Python 3.5 and newer (and 2.7).

* appveyor: replace --slowest with --slow

* Travis CI: remove the GCC coverage job

* Travis CI: remove tzdata resource from regrtest

tzdata resource doesn't exist in Python 3.4.

* Travis CI: remove the doc job

Fixing Sphinx warnings requires to backport huge intrusive changes
like:

- commit d97b7dc94b19063f0589d401bdc4aaadc7030762
- commit 5c6793394066b012b9674681b0815667938ce4d9

* appveyor: set version to 3.4.6+

* bpo-30730: Fix test_os tests.

Fix test_invalid_cmd() and test_invalid_env(), TypeError is raised on
Python 3.4.

(cherry picked from commit 5e22721e586344b547194f0f7ea67fd425f94e72)