Bump version to v0.4

Change-Id: I50c63ff8219a6982e0bbc34a939ce274dbacf976
diff --git a/script/korapxml2conllu b/script/korapxml2conllu
index 494b490..b62cc3d 100755
--- a/script/korapxml2conllu
+++ b/script/korapxml2conllu
@@ -17,7 +17,7 @@
 my %plain_texts;
 my %sentence_ends;
 
-our $VERSION = '0.3.900';
+our $VERSION = '0.4';
 
 our $VERSION_MSG = "\nkorapxml2conllu - v$VERSION\n";