MINOR: contrib/spoa_server: Upgrade SPOP to 2.0

Upgrade SPOP version to 2.0
diff --git a/contrib/spoa_server/spoa.h b/contrib/spoa_server/spoa.h
index ee19f37..e9a7a46 100644
--- a/contrib/spoa_server/spoa.h
+++ b/contrib/spoa_server/spoa.h
@@ -18,7 +18,7 @@
 #include <sys/time.h>
 
 #define MAX_FRAME_SIZE    16384
-#define SPOP_VERSION      "1.0"
+#define SPOP_VERSION      "2.0"
 #define SPOA_CAPABILITIES ""
 
 /* All supported data types */