Implement 1_8 writing

src/main/java/us/myles/ViaVersion/api/type/types/version/Metadata1_8Type.java

@@ -19,7 +19,9 @@ public class Metadata1_8Type extends MetaTypeTemplate {
     }
 
     @Override
-    public void write(ByteBuf buffer, Metadata object) throws Exception {
+    public void write(ByteBuf buffer, Metadata meta) throws Exception {
-        throw new UnsupportedOperationException("1.8 Metadata writing is not implemented!");
+        byte item = (byte) (meta.getTypeID() << 5 | meta.getId() & 0x1F);
+        buffer.writeByte(item);
+        meta.getType().write(buffer, meta.getValue());
     }
 }

src/main/java/us/myles/ViaVersion/api/type/types/version/MetadataList1_8Type.java

@@ -25,6 +25,8 @@ public class MetadataList1_8Type extends MetaListTypeTemplate {
 
     @Override
     public void write(ByteBuf buffer, List<Metadata> object) throws Exception {
-        throw new UnsupportedOperationException("1.8 MetadataList writing is not implemented");
+        for (Metadata data : object)
+            Types1_8.METADATA.write(buffer, data);
+        buffer.writeByte(127);
     }
 }