Drop support for Unity 4, to support push notifications.
Drop support for Unity 4, to support push notifications.

Push notifications on Unity 5 were broken due to IL2CPP not supporting PropertyInfo being exported by any type.

Fixes #36.

wujun4code/Parse-SDK-dotNET,wujun4code/Parse-SDK-dotNET,ParsePlatform/Parse-SDK-dotNET,ParsePlatform/Parse-SDK-dotNET,AmeliaMesdag/Parse-SDK-dotNET,AmeliaMesdag/Parse-SDK-dotNET