Add grunt for building

.gitignore

 node_modules/
+index.js

Gruntfile.js

+module.exports = function (grunt) {
+	grunt.loadNpmTasks('grunt-babel');
+
+	grunt.initConfig({
+		babel: {
+			dist: {
+				files: {
+					'index.js': 'src/index.js'
+				}
+			}
+		}
+	});
+
+	grunt.registerTask('default', ['babel']);
+};

package.json

 {
   "name": "ed3-format-default",
-  "version": "0.2.1",
+  "version": "0.2.4",
   "description": "Default format for ed3 library",
   "main": "index.js",
   "scripts": {
@@ -13,13 +13,14 @@
   "author": "missingdays",
   "license": "ISC",
   "dependencies": {
-    "d3": "^4.2.0",
     "excel-style-dataformatter": "^1.0.3"
   },
   "devDependencies": {
     "babel-preset-es2015": "^6.13.2",
     "babel-register": "^6.11.6",
     "expect.js": "^0.3.1",
+    "grunt": "1.0.1",
+    "grunt-babel": "6.0.0",
     "mocha": "^3.0.0"
   }
 }