ci: fix travis cleanup

Author: henryiii

.travis.yml

@@ -32,7 +32,7 @@ deploy:
   provider: pypi
   distributions: "--license" # Trick travis, see https://github.com/travis-ci/dpl/blob/577fb987337b6275f85cc104a38df30d030a860e/lib/dpl/providers/pypi.rb#L36
   username: "__token__"
-  skip_cleanup: false
+  skip_cleanup: true
   on:
     tags: true
   password:

CONTRIBUTING.md

@@ -193,7 +193,7 @@ end
 
 - Finish merging open PRs that you want in the new version
 - Add most recent changes to the `docs/CHANGELOG.md`
-- Sync master with develop using `git merge develop --ff-only` and push
+- Sync master with develop using `git checkout master; git merge develop --ff-only` and push
 - Make sure the full wheel build runs on master without issues (will happen
   automatically on push to master)
 - Make the GitHub release in the GitHub UI. Copy the changelog entries and