Bump version to 2.3.1

Change-Id: Ia081aea7a7a842402c3f3edbbd9e510ca288eb46
diff --git a/script/tei2korapxml b/script/tei2korapxml
index e7ffd17..7838bab 100755
--- a/script/tei2korapxml
+++ b/script/tei2korapxml
@@ -29,7 +29,7 @@
   1;
 };
 
-our $VERSION = '2.3.0';
+our $VERSION = '2.3.1';
 
 our $VERSION_MSG = "\ntei2korapxml - v$VERSION\n";