remove trailing whitespace

Author: mbostock

package.json

@@ -23,7 +23,7 @@
   "files": [
     "dist/**/*.js",
     "src/**/*.js",
-    "src/**/*.css"    
+    "src/**/*.css"
   ],
   "scripts": {
     "test": "mkdir -p test/output && mocha -r module-alias/register 'test/**/*-test.js' && mocha -r module-alias/register test/plot.js && eslint src test",