Install in install step

Ray Schamp · Ray Schamp · commit 414f14e39279 · 2017-06-02T08:52:45.000-04:00
`npm update` didn't install eslint on https://travis-ci.org/LLK/scratch-storage/jobs/238734818
diff --git a/.travis.yml b/.travis.yml
@@ -7,6 +7,7 @@ node_js:
   - "4"
   - "node"
 install:
+  - npm install
   - npm update
   - npm prune
 script:
