Update proguard-square-retrofit.pro

The proguard file for retrofit is incomplete. It does not support rest service interfaces with callbacks and error handling. This PR adds support for that.

Author: SandroMachado

libraries/proguard-square-retrofit.pro

@@ -1,11 +1,23 @@
+# Retrofit 1.X
+
 -keep class com.squareup.okhttp.** { *; }
+-keep class retrofit.** { *; }
 -keep interface com.squareup.okhttp.** { *; }
--dontwarn com.squareup.okhttp.**
 
--dontwarn rx.**
--dontwarn retrofit.**
+-dontwarn com.squareup.okhttp.**
 -dontwarn okio.**
--keep class retrofit.** { *; }
+-dontwarn retrofit.**
+-dontwarn rx.**
+
 -keepclasseswithmembers class * {
  @retrofit.http.* <methods>;
-}
+}
+
+# If in your rest service interface you use methods with Callback argument.
+-keepattributes Exceptions
+
+# If your rest service methods throw custom exceptions, because you've defined an ErrorHandler.
+-keepattributes Signature
+
+# Also you must note that if you are using GSON for conversion from JSON to POJO representation, you must ignore those POJO classes from being obfuscated.
+# Here include the POJO's that have you have created for mapping JSON response to POJO for example.