Updated proguard.cfg example to Gson only settings

Fixed https://github.com/google/gson/issues/713

examples/android-proguard-example/proguard.cfg

@@ -1,77 +1,3 @@
-##---------------Begin: proguard configuration common for all Android apps ----------
--optimizationpasses 5
--dontusemixedcaseclassnames
--dontskipnonpubliclibraryclasses
--dontskipnonpubliclibraryclassmembers
--dontpreverify
--verbose
--dump class_files.txt
--printseeds seeds.txt
--printusage unused.txt
--printmapping mapping.txt
--optimizations !code/simplification/arithmetic,!field/*,!class/merging/*
-
--allowaccessmodification
--keepattributes *Annotation*
--renamesourcefileattribute SourceFile
--keepattributes SourceFile,LineNumberTable
--repackageclasses ''
-
--keep public class * extends android.app.Activity
--keep public class * extends android.app.Application
--keep public class * extends android.app.Service
--keep public class * extends android.content.BroadcastReceiver
--keep public class * extends android.content.ContentProvider
--keep public class * extends android.app.backup.BackupAgentHelper
--keep public class * extends android.preference.Preference
--keep public class com.android.vending.licensing.ILicensingService
--dontnote com.android.vending.licensing.ILicensingService
-
-# Explicitly preserve all serialization members. The Serializable interface
-# is only a marker interface, so it wouldn't save them.
--keepclassmembers class * implements java.io.Serializable {
-    static final long serialVersionUID;
-    private static final java.io.ObjectStreamField[] serialPersistentFields;
-    private void writeObject(java.io.ObjectOutputStream);
-    private void readObject(java.io.ObjectInputStream);
-    java.lang.Object writeReplace();
-    java.lang.Object readResolve();
-}
-
-# Preserve all native method names and the names of their classes.
--keepclasseswithmembernames class * {
-    native <methods>;
-}
-
--keepclasseswithmembernames class * {
-    public <init>(android.content.Context, android.util.AttributeSet);
-}
-
--keepclasseswithmembernames class * {
-    public <init>(android.content.Context, android.util.AttributeSet, int);
-}
-
-# Preserve static fields of inner classes of R classes that might be accessed
-# through introspection.
--keepclassmembers class **.R$* {
-  public static <fields>;
-}
-
-# Preserve the special static methods that are required in all enumeration classes.
--keepclassmembers enum * {
-    public static **[] values();
-    public static ** valueOf(java.lang.String);
-}
-
--keep public class * {
-    public protected *;
-}
-
--keep class * implements android.os.Parcelable {
-  public static final android.os.Parcelable$Creator *;
-}
-##---------------End: proguard configuration common for all Android apps ----------
-
 ##---------------Begin: proguard configuration for Gson  ----------
 # Gson uses generic type information stored in a class file when working with fields. Proguard
 # removes such information by default, so configure it to keep all of it.