Fix reset of current metadata index

Before, the index of seen metadata was always 0 after heaving read all
metadata.

Change-Id: I941d7e4d8dc01d5d34053344c25cda637fb24b68
diff --git a/src/dereko2vec.c b/src/dereko2vec.c
index 48b4480..33b8d03 100644
--- a/src/dereko2vec.c
+++ b/src/dereko2vec.c
@@ -822,10 +822,10 @@
 				if (is_metadata) {
 					if (debug_mode > 1)
 						printf("Metadata: %s\n", vocab[word].word);
-					metadata[metadata_index++] = word;
 					if (metadata_index >= metadata_categories) {
 						metadata_index = 0;
 					}
+					metadata[metadata_index++] = word;
 					continue;
 				}
 				if (feof(fi))