build bootstrap in esm

js/tests/integration/bundle.js

@@ -1,7 +1,9 @@
 import 'popper.js'
-import bootstrap from '../../../dist/js/bootstrap'
+import {
+  Tooltip
+} from '../../../dist/js/bootstrap.esm.js'
 
 window.addEventListener('load', () => {
   [...document.querySelectorAll('[data-toggle="tooltip"]')]
-    .map(tooltipNode => new bootstrap.Tooltip(tooltipNode))
+    .map(tooltipNode => new Tooltip(tooltipNode))
 })

js/tests/integration/rollup.bundle.js

@@ -1,7 +1,6 @@
 /* eslint-env node */
 
 const resolve = require('rollup-plugin-node-resolve')
-const commonjs = require('rollup-plugin-commonjs')
 const babel = require('rollup-plugin-babel')
 
 module.exports = {
@@ -12,7 +11,6 @@ module.exports = {
   },
   plugins: [
     resolve(),
-    commonjs(),
     babel({
       exclude: 'node_modules/**'
     })