Update Rollup.

package.json

@@ -26,7 +26,7 @@
     "pretest": "rm -rf build && mkdir build && rollup --banner \"$(preamble)\" -g d3-dispatch:d3,d3-selection:d3 -f umd -n d3 -o build/d3-drag.js -- index.js",
     "test": "tape 'test/**/*-test.js' && eslint index.js src",
     "prepublish": "npm run test && uglifyjs --preamble \"$(preamble)\" build/d3-drag.js -c -m -o build/d3-drag.min.js",
-    "postpublish": "VERSION=`node -e 'console.log(require(\"./package.json\").version)'`; git push && git push --tags && cd ../d3.github.com && git pull && cp ../d3-drag/build/d3-drag.js d3-drag.v1.js && cp ../d3-drag/build/d3-drag.min.js d3-drag.v1.min.js && git add d3-drag.v1.js d3-drag.v1.min.js && git commit -m \"d3-drag ${VERSION}\" && git push && cd - && zip -j build/d3-drag.zip -- LICENSE README.md build/d3-drag.js build/d3-drag.min.js"
+    "postpublish": "git push && git push --tags && cd ../d3.github.com && git pull && cp ../d3-drag/build/d3-drag.js d3-drag.v1.js && cp ../d3-drag/build/d3-drag.min.js d3-drag.v1.min.js && git add d3-drag.v1.js d3-drag.v1.min.js && git commit -m \"d3-drag ${npm_package_version}\" && git push && cd - && zip -j build/d3-drag.zip -- LICENSE README.md build/d3-drag.js build/d3-drag.min.js"
   },
   "dependencies": {
     "d3-dispatch": "1",
@@ -35,7 +35,7 @@
   "devDependencies": {
     "eslint": "3",
     "package-preamble": "0.0",
-    "rollup": "0.36",
+    "rollup": "0.41",
     "tape": "4",
     "uglify-js": "2"
   }