Revert to npm install from npm ci

Due to TravisCI issues:

0.49s$ npm ci
npm ERR! Unexpected string in JSON at position 609390
npm ERR! A complete log of this run can be found in:
npm ERR!     /home/travis/.npm/_logs/2018-07-25T19_59_42_628Z-debug.log
The command "npm ci" failed and exited with 1 during .

Author: interactivellama

.travis.yml

@@ -5,7 +5,7 @@ node_js:
 install:
   - npm install npm -g
   - npm config set audit false
-  - npm ci
+  - npm install
 script:
   - npm run travis-ci
 env: