Make Metadata class public

Author: oschwald

src/main/java/com/maxmind/db/Metadata.java

@@ -10,7 +10,7 @@
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
-final class Metadata {
+public final class Metadata {
     private final int binaryFormatMajorVersion;
     private final int binaryFormatMinorVersion;