Add dist/unfetch.es.js output and point modules/jsnext:main at it. F…

…ixes #25.

package.json

@@ -2,16 +2,17 @@
   "name": "unfetch",
   "version": "2.0.1",
   "description": "Bare minimum fetch polyfill in 500 bytes",
-  "module": "src/index.js",
-  "jsnext:main": "src/index.js",
   "main": "dist/unfetch.js",
+  "module": "dist/unfetch.es.js",
+  "jsnext:main": "dist/unfetch.es.js",
   "umd:main": "dist/unfetch.umd.js",
   "scripts": {
     "test": "eslint src test && mocha --compilers js:babel-register test/**/*.js",
-    "build": "npm-run-all clean -p rollup:* -p minify:* -s size",
+    "build": "npm-run-all --silent clean -p rollup:* -p minify:* -s size",
     "clean": "rimraf dist && mkdirp dist",
-    "rollup:cjs": "cross-env FORMAT=cjs rollup -c rollup.config.js -m -f cjs -n $npm_package_name $npm_package_module -o $npm_package_main",
-    "rollup:umd": "rollup -c rollup.config.js -m -f umd -n $npm_package_name $npm_package_module -o $npm_package_umd_main",
+    "rollup:cjs": "cross-env FORMAT=cjs rollup -c rollup.config.js -f cjs -n $npm_package_name -o $npm_package_main",
+    "rollup:umd": "cross-env FORMAT=umd rollup -c rollup.config.js -f umd -n $npm_package_name -o $npm_package_umd_main",
+    "rollup:esm": "rollup -c rollup.config.js -f es -n $npm_package_name -o $npm_package_module",
     "minify:cjs": "uglifyjs $npm_package_main -cm toplevel -o $npm_package_main -p relative --in-source-map ${npm_package_main}.map --source-map ${npm_package_main}.map",
     "minify:umd": "uglifyjs $npm_package_umd_main -cm -o $npm_package_umd_main -p relative --in-source-map ${npm_package_umd_main}.map --source-map ${npm_package_umd_main}.map",
     "size": "echo \"Gzipped Size: $(strip-json-comments --no-whitespace $npm_package_main | gzip-size)\"",

rollup.config.js

@@ -1,18 +1,21 @@
 import buble from 'rollup-plugin-buble';
 import replace from 'rollup-plugin-post-replace';
 
+let { FORMAT } = process.env;
+
 export default {
 	useStrict: false,
+	sourceMap: true,
+	entry: 'src/index.js',
 	plugins: [
 		buble(),
-		replace(
-			process.env.FORMAT==='cjs' ? {
-				'module.exports = index;': '',
-				'var index =': 'module.exports ='
-			} : {
-				'return index;': '',
-				'var index =': 'return'
-			}
-		)
+		FORMAT==='cjs' && replace({
+			'module.exports = index;': '',
+			'var index =': 'module.exports ='
+		}),
+		FORMAT==='umd' && replace({
+			'return index;': '',
+			'var index =': 'return'
+		})
 	]
 };