Update to popper.js v2.x

js/tests/karma.conf.js

@@ -5,6 +5,7 @@ const ip = require('ip')
 const { babel } = require('@rollup/plugin-babel')
 const istanbul = require('rollup-plugin-istanbul')
 const { nodeResolve } = require('@rollup/plugin-node-resolve')
+const replace = require('@rollup/plugin-replace')
 
 const {
   browsers,
@@ -74,6 +75,9 @@ const conf = {
   },
   rollupPreprocessor: {
     plugins: [
+      replace({
+        'process.env.NODE_ENV': '"dev"'
+      }),
       istanbul({
         exclude: [
           'node_modules/**',