Switch lib-jitsi-meet from Browserify to Webpack

Since the library lib-jitsi-meet does not publish its binaries, it is
always been necessary to produce the binaries i.e. lib-jitsi-meet.js and
lib-jitsi-meet.js as part of the npm install step. Which means that any
modifications to the devDependencies of lib-jitsi-meet's package.json
always have to be reflected in jitsi-meet's package.json. Because
Webpack replaced Browserify in lib-jitsi-meet, Webpack has to become a
devDependency of jitsi-meet.

package.json

     "jshint": "2.8.0",
     "node-sass": "^3.8.0",
     "precommit-hook": "3.0.0",
-    "uglify-js": "2.4.24"
+    "uglify-js": "2.4.24",
+
+    "babel-core": "*",
+    "babel-loader": "*",
+    "babel-register": "*",
+    "string-replace-loader": "*",
+    "webpack": "*"
   },
   "license": "Apache-2.0",
   "scripts": {