chore: Dropped support of Node.js 4

Some NPM dependencies dropped support of Node.js 4. It is easier to drop it
too, that looking for workarounds to get the testing build running, or claim
the support without actually testing it.

Add testing with Node.js 10.

BREAKING CHANGE: Dropped support of Node.js 4

Author: prantlf

.travis.yml

@@ -6,9 +6,9 @@ cache:
 notifications:
   email: false
 node_js:
+  - '10'
   - '8'
   - '6'
-  - '4'
 after_success:
   - npm run travis-deploy-once "npm run semantic-release"
 branches:

README.md

@@ -198,6 +198,7 @@ your code using Grunt.
 
 ## Release History
 
+ * 2018-04-27   v3.0.0   Dropped support of Node.js 4
  * 2018-03-05   v2.2.0   Upgrade to the reporter v2.2.0, allow generating
                          page titles from file names without directory
  * 2018-03-04   v2.1.0   Upgrade to the reporter v2.1.0

package.json

@@ -23,23 +23,23 @@
     }
   ],
   "engines": {
-    "node": ">= 4"
+    "node": ">= 6"
   },
   "scripts": {
     "test": "grunt",
     "semantic-release": "semantic-release",
     "travis-deploy-once": "travis-deploy-once"
   },
   "dependencies": {
-    "chalk": "^2.3.2",
-    "grunt-html-html-reporter": "^2.2.0"
+    "chalk": "^2.4.1",
+    "grunt-html-html-reporter": "^3.0.0"
   },
   "devDependencies": {
     "grunt": "^1.0.2",
     "grunt-contrib-clean": "^1.1.0",
     "grunt-contrib-nodeunit": "^1.0.0",
     "grunt-standard": "^3.1.0",
-    "semantic-release": "^15.1.5",
+    "semantic-release": "^15.1.7",
     "travis-deploy-once": "^4.4.1"
   },
   "peerDependencies": {