Merge pull request #234 from adjust/docs-update

Docs update

README.md

@@ -213,7 +213,7 @@ If you encounter any issues getting the Google advertising ID, please open an is
 If you are using Proguard, add these lines to your Proguard file:
 
 ```
--keep public class com.adjust.sdk.** { *; }
+-keep class com.adjust.sdk.** { *; }
 -keep class com.google.android.gms.common.ConnectionResult {
     int SUCCESS;
 }