Hide deploy job from CI unless commit is tagged

[webknjaz]

Ref travis-ci/beta-features#28
Ref https://blog.travis-ci.com/2017-09-12-build-stages-order-and-conditions
Ref https://docs.travis-ci.com/user/conditional-builds-stages-jobs#Specifying-conditions

/cc: @asvetlov

[codecov-io]

Codecov Report

Merging #2269 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2269   +/-   ##
=======================================
  Coverage   97.31%   97.31%           
=======================================
  Files          39       39           
  Lines        7945     7945           
  Branches     1378     1378           
=======================================
  Hits         7732     7732           
  Misses         90       90           
  Partials      123      123

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9d7c28b...2d9732d. Read the comment docs.

[lock]

This thread has been automatically locked since there has not been
any recent activity after it was closed. Please open a new issue for
related bugs.

If you feel like there's important points made in this discussion,
please include those exceprts into that new issue.