* Backport Travis CI config from master

Add .travis.yml for Travis CI.

* 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 7895a058)