Add babel to build

package.json

@@ -1,6 +1,6 @@
 {
   "name": "d3-bumps-chart",
-  "version": "0.0.1",
+  "version": "0.0.2",
   "description": "Draw bumps charts.",
   "keywords": [
     "d3",
@@ -21,7 +21,7 @@
     "url": "https://github.com/johnwalley/d3-bumps-chart.git"
   },
   "scripts": {
-    "pretest": "rm -rf build && mkdir build && rollup --banner \"$(preamble)\" -f umd -g d3:d3 -n bumpsChart -o build/d3-bumps-chart.js -- index.js",
+    "pretest": "rm -rf build && mkdir build && rollup -c --banner \"$(preamble)\" -f umd -g d3:d3 -n bumpsChart -o build/d3-bumps-chart.js -- index.js",
     "test": "tape 'test/**/*-test.js' && eslint index.js src",
     "prepublish": "npm run test && uglifyjs --preamble \"$(preamble)\" build/d3-bumps-chart.js -c -m -o build/d3-bumps-chart.min.js",
     "postpublish": "zip -j build/d3-bumps-chart.zip -- LICENSE README.md build/d3-bumps-chart.js build/d3-bumps-chart.min.js"
@@ -30,10 +30,12 @@
     "d3": "^4.2.2"
   },
   "devDependencies": {
+    "babel-preset-es2015-rollup": "^1.2.0",
     "eslint": "2",
-    "package-preamble": "0.0",
+    "package-preamble": "0.0.2",
     "rollup": "0.34",
+    "rollup-plugin-babel": "^2.6.1",
     "tape": "4",
-    "uglify-js": "2"
+    "uglify-js": "^2.7.3"
   }
 }

rollup.config.js

@@ -0,0 +1,8 @@
+import babel from 'rollup-plugin-babel';
+
+export default {
+  entry: 'src/main.js',
+  format: 'cjs',
+  plugins: [ babel() ],
+  dest: 'bundle.js'
+};

src/.babelrc

@@ -0,0 +1,3 @@
+{
+  "presets": ["es2015-rollup"]
+}