Migrate to travis-ci.com

Oleksandr Porunov <alexand...@...>

Currently we are using travis-ci.org and I often notice periodic problems with that. Sometimes workers stop to process any computation, sometimes website doesn't work (on maintenance), sometimes ability to restart jobs disappear and I need to sign out and then sign in to fix that.
I don't know if those problems will occur when switching to `.com` but at least I noticed last time that when `.org` was under maintenance, `.com` version was working properly.
I would suggest to give it a try and use `.com` version for a while to check if it will work better for our use cases.

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