The latest node 8 includes an updated npm already.

timdorr · web-flow · commit 775765ab2ce4 · 2017-12-07T12:40:05.000-05:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,8 +1,6 @@
 language: node_js
 node_js:
   - "8"
-before_install:
-  - npm i -g npm
 script:
   - npm run lint
   - npm run test:cov
