Add rollup.config.

package.json

@@ -34,7 +34,7 @@
     "url": "https://github.com/d3/d3-dsv.git"
   },
   "scripts": {
-    "pretest": "rm -rf build && mkdir build && rollup --banner \"$(preamble)\" -f umd -n d3 --extend -o build/d3-dsv.js -- index.js",
+    "pretest": "rm -rf build && mkdir build && rollup -c --banner \"$(preamble)\"",
     "test": "tape 'test/**/*-test.js' && eslint index.js src",
     "prepublish": "npm run test && uglifyjs -b beautify=false,preamble=\"'$(preamble)'\" build/d3-dsv.js -c -m -o build/d3-dsv.min.js",
     "postpublish": "git push && git push --tags && cd ../d3.github.com && git pull && cp ../d3-dsv/build/d3-dsv.js d3-dsv.v1.js && cp ../d3-dsv/build/d3-dsv.min.js d3-dsv.v1.min.js && git add d3-dsv.v1.js d3-dsv.v1.min.js && git commit -m \"d3-dsv ${npm_package_version}\" && git push && cd - && zip -j build/d3-dsv.zip -- LICENSE README.md build/d3-dsv.js build/d3-dsv.min.js"

rollup.config.js

@@ -0,0 +1,9 @@
+export default {
+  input: "index",
+  output: {
+    extend: true,
+    file: "build/d3-dsv.js",
+    format: "umd",
+    name: "d3"
+  }
+};