docs dir conflicts from travis

[7yl4r]

Reported by @eqmh : Because travis pushes on the master branch sometimes you can get unexpected merge conflicts. This article describes the problem well (although I disagree with the conclusion).

marinebon/condition-reports force-pushes over a gh-pages branch, but that requires some weird build steps rather than nicely building into ./docs. I would like a better option, but I don't have any examples.

Best way might be to use the actual travis.yml deployment instead of the manual git commands. I think that would look something like:

deploy:
  local-dir: ./docs
  provider: pages
  skip-cleanup: true
  github-token: $GH_TOKEN
  target-branch: gh-pages
  on:
    branch: master

after doing this is would also make sense to add ./docs to the .gitignore