Build: Remove deprecated option and enable caching (#51)

RDIL · joyeecheung · commit fccec73d5899 · 2019-03-24T10:30:16.000+08:00
Makes future master branch builds faster
diff --git a/.travis.yml b/.travis.yml
@@ -3,4 +3,4 @@ node_js:
   - "8"
   - "10"
   - "11"
-sudo: false
+cache: npm
