No longer run Node.js v4 on Travis

- Jasmine should still work in Node.js v4, but the jshint task isn't
  working correctly

.travis.yml

@@ -22,9 +22,6 @@ addons:
 
 matrix:
   include:
-    - env:
-      - USE_SAUCE=false
-      - TEST_COMMAND="bash travis-node-script.sh v4"
     - env:
       - USE_SAUCE=false
       - TEST_COMMAND="bash travis-node-script.sh v8"

Gruntfile.js

@@ -16,12 +16,6 @@ module.exports = function(grunt) {
 
   grunt.registerTask('default', ['jshint:all']);
 
-  if (/^v4\./.test(process.version)) {
-    grunt.registerTask('jshint', function() {
-      console.log('Skipping jshint for older versions of Node');
-    });
-  }
-
   var version = require('./grunt/tasks/version.js');
 
   grunt.registerTask('build:copyVersionToGem',