Merge pull request #10 from fh1ch/chore/travis-npm-fix

chore(npm): switch from yarn to npm to prevent issues with Travis

Author: fh1ch

.travis.yml

@@ -1,11 +1,9 @@
 language: "node_js"
 node_js:
-  - "5"
+  - "10"
+  - "8"
+  - "6"
   - "4"
-  - "3"
-  - "2"
-  - "1"
-  - "0.12"
 
 before_install:
   - "npm install coveralls"