Add webpack 2 RC compatibility

Author: SpaceK33z

package.json

@@ -4,7 +4,7 @@
   "author": "Tobias Koppers @sokra",
   "description": "Extract text from bundle into a file.",
   "peerDependencies": {
-    "webpack": "^2.1.0-beta.19"
+    "webpack": "^2.1.0-beta.19 || ^2.2.0-rc.0"
   },
   "dependencies": {
     "async": "^2.1.2",