Test out building in diff node version than test

.travis.yml

@@ -7,7 +7,14 @@ node_js:
   - "5"
   - "6"
 
-before_script: 'if [ -n "${BABEL-}" ]; then make bootstrap-babel ; fi'
+before_install:
+  - . $HOME/.nvm/nvm.sh
+  - nvm install stable && nvm use stable
+
+before_script:
+  - 'if [ -n "${BABEL-}" ]; then make bootstrap-babel ; fi'
+  - 'npm run build'
+  - 'nvm use $TRAVIS_NODE_VERSION; echo "Switched to node $TRAVIS_NODE_VERSION"'
 
 script:
   - 'if [ -n "${LINT-}" ]; then npm run lint ; fi'

package.json

@@ -46,7 +46,7 @@
     "preversion": "npm run test && npm run changelog",
     "test": "npm run lint && npm run flow && npm run build && npm run test-only",
     "test-only": "ava test",
-    "test-ci": "cross-env BABEL_ENV=test npm run build && nyc npm run test-only",
+    "test-ci": "cross-env BABEL_ENV=test nyc npm run test-only",
     "changelog": "git log `git describe --tags --abbrev=0`..HEAD --pretty=format:' * %s (%an)' | grep -v 'Merge pull request'"
   },
   "nyc": {