Import helpers like __extends from tslib.

This reduces the minified size of lib/react-apollo.umd.js from 28074B to
22773B (18.9%). The minified+gzip size drops from 6930B to 6451B (6.9%).

The gzip percentage is smaller because there was some repetition between
the multiple declarations of the __extends function, and gzip is good at
compressing long repeated substrings.

package.json

@@ -153,6 +153,7 @@
     "hoist-non-react-statics": "^3.0.0",
     "invariant": "^2.2.2",
     "lodash.isequal": "^4.5.0",
-    "prop-types": "^15.6.0"
+    "prop-types": "^15.6.0",
+    "tslib": "^1.9.3"
   }
 }

rollup.config.js

@@ -11,55 +11,39 @@ function onwarn(message) {
   }
 }
 
-export default [
-  // for browser
-  {
-    input: 'lib/browser.js',
+function umd(inputFile, outputFile) {
+  return {
+    input: inputFile,
     output: {
-      file: 'lib/react-apollo.browser.umd.js',
+      file: outputFile,
       format: 'umd',
       name: 'react-apollo',
       sourcemap: true,
       exports: 'named',
     },
+    plugins: [
+      node({
+        module: true,
+        only: ['tslib']
+      })
+    ],
     onwarn,
-  },
+  };
+}
+
+export default [
+  // for browser
+  umd("lib/browser.js",
+      "lib/react-apollo.browser.umd.js"),
   // for server
-  {
-    input: 'lib/index.js',
-    output: {
-      file: 'lib/react-apollo.umd.js',
-      format: 'umd',
-      name: 'react-apollo',
-      sourcemap: false,
-      exports: 'named',
-    },
-    onwarn,
-  },
+  umd("lib/index.js",
+      "lib/react-apollo.umd.js"),
   // for test-utils
-  {
-    input: 'lib/test-utils.js',
-    output: {
-      file: 'lib/test-utils.js',
-      format: 'umd',
-      name: 'react-apollo',
-      sourcemap: false,
-      exports: 'named',
-    },
-    onwarn,
-  },
+  umd("lib/test-utils.js",
+      "lib/test-utils.js"),
   // for test-links
-  {
-    input: 'lib/test-links.js',
-    output: {
-      file: 'lib/test-links.js',
-      format: 'umd',
-      name: 'react-apollo',
-      sourcemap: false,
-      exports: 'named',
-    },
-    onwarn,
-  },
+  umd("lib/test-links.js",
+      "lib/test-links.js"),
   // for filesize
   {
     input: 'lib/react-apollo.browser.umd.js',

tsconfig.json

@@ -6,6 +6,7 @@
     "lib": ["es2015", "dom"],
     "module": "es2015",
     "moduleResolution": "node",
+    "importHelpers": true,
     "noUnusedParameters": true,
     "outDir": "lib",
     "pretty": true,