Just bump to Node 6, to match our Windows support.

Author: chriskrycho

.travis.yml

@@ -1,9 +1,7 @@
 ---
 language: node_js
 node_js:
-  # we recommend testing addons with the same minimum supported node version as Ember CLI
-  # so that your addon works for all apps
-  - "4"
+  - "6"
 
 sudo: false
 dist: trusty

index.js

@@ -1,4 +1,3 @@
-'use strict';
 /* eslint-env node */
 
 const fs = require('fs');

lib/typescript-preprocessor.js

@@ -1,4 +1,3 @@
-'use strict';
 /* eslint-env node */
 const fs = require('fs');
 const path = require('path');