Pulling logic from .travis.yml into scripts.
Cleaned up scripts and added ci/travis folder.

- created ci/travis/ for only travis-ci scripts
- renamed scripts to match `<travis-directive>-<action>-<os>.sh` (where os
  is optional when scripts will run in all OSes, and action is optional
if there is only one action per directive).
Merge pull request #1250 from rhyolight/clean-travis-scripts

Pulling logic from .travis.yml into scripts.