remove node 5 in travis.yml (#143)

Since Node 5 is past its useful life, speed up the build process by just specifying LTS versions 4 and 6.

* Remove sudo: false from .travis

* Remove whitespace

Author: JaKXz

.travis.yml

@@ -1,7 +1,6 @@
 language: node_js
 node_js:
   - "6"
-  - "5"
   - "4"
 script:
   - npm run lint