Update README.md

Author: Redth

README.md

@@ -1,9 +1,11 @@
-PushSharp v3.0
+PushSharp v4.0
 ==============
 
 PushSharp is a server-side library for sending Push Notifications to iOS/OSX (APNS), Android/Chrome (GCM), Windows/Windows Phone, Amazon (ADM) and Blackberry devices!
 
-PushSharp v3.0 is a complete rewrite of the original library, aimed at taking advantage of things like async/await, HttpClient, and generally a better infrastructure using lessons learned from the old code.
+PushSharp v4.0+ is a complete rewrite of the original library, aimed at taking advantage of things like async/await, HttpClient, and generally a better infrastructure using lessons learned from the old code.
+
+PushSharp will now follow [semver](http://semver.org/) versioning, so major version numbers will go up as there are any breaking api changes. 
 
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