chore(readme): fix webpack update version typo

Close angular#2200

Author: dzonatan

README.md

@@ -18,11 +18,11 @@ If you wish to collaborate while the project is still young, check out [our issu
 
 ## Webpack update
 
-We changed the build system between beta.10 and beta.12, from SystemJS to Webpack. 
+We changed the build system between beta.10 and beta.14, from SystemJS to Webpack. 
 And with it comes a lot of benefits. 
 To take advantage of these, your app built with the old beta will need to migrate.
 
-You can update your `beta.10` projects to `beta.12` by following [these instructions](https://github.com/angular/angular-cli/wiki/Upgrading-from-Beta.10-to-Beta.14).
+You can update your `beta.10` projects to `beta.14` by following [these instructions](https://github.com/angular/angular-cli/wiki/Upgrading-from-Beta.10-to-Beta.14).
 
 ## Prerequisites