Flip the logic, and publish to a develop channel

The latest tag now is stable, and if you want the build from develop you can use `@develop` for that.

.travis.yml

@@ -9,7 +9,7 @@ env:
   global:
   - NODE_ENV=production
   - SMOKE_URL=https://llk.github.io/scratch-gui/$TRAVIS_PULL_REQUEST_BRANCH
-  - NPM_TAG=preview
+  - NPM_TAG=latest
 cache:
   directories:
   - node_modules
@@ -21,7 +21,7 @@ script:
 - if [ "$TRAVIS_EVENT_TYPE" == "pull_request" ] && [ "$TRAVIS_BRANCH" == "master" ]; then  npm run test:smoke; fi
 before_deploy:
 - npm --no-git-tag-version version 0.1.0-prerelease.$(date +%Y%m%d%H%M%S)
-- if [ "$TRAVIS_BRANCH" == "develop" ]; then export NPM_TAG=latest; fi
+- if [ "$TRAVIS_BRANCH" == "develop" ]; then export NPM_TAG=develop; fi
 - git config --global user.email $(git log --pretty=format:"%ae" -n1)
 - git config --global user.name $(git log --pretty=format:"%an" -n1)
 deploy:
@@ -42,7 +42,6 @@ deploy:
     - master
     - develop
     - smoke
-    - npm-preview-channel
   skip_cleanup: true
   email: $NPM_EMAIL
   api_key: $NPM_TOKEN