Changed an inclusion path

I've also modified my local SDL_net install to ensure that it built with the correct version of
SDL. Long story short: This worked me up way too much.

network/packet_types/serial_packet_base.hpp

@@ -23,7 +23,7 @@
 
 #include "serial_packet_type.hpp"
 
-#include "SDL_net.h"
+#include "SDL2/SDL_net.h"
 
 constexpr int PACKET_STRING_SIZE = 100;
 

network/udp_network_utility.hpp

@@ -26,7 +26,7 @@
 #include "singleton.hpp"
 
 //APIs
-#include "SDL_net.h"
+#include "SDL2/SDL_net.h"
 
 class UDPNetworkUtility : public Singleton<UDPNetworkUtility> {
 public: