Bump version to 2.3.1

Change-Id: I858cc6b31e9cbcab88f4cff080e19e8b861ec6cb
diff --git a/pom.xml b/pom.xml
index 85369ff..dd28bf4 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
 
     <groupId>de.ids-mannheim.korap.tokenizer</groupId>
     <artifactId>KorAP-Tokenizer</artifactId>
-    <version>2.3.1-SNAPSHOT</version>
+    <version>2.3.1</version>
 
     <name>KorAP-Tokenizer</name>
     <description>DFA tokenizer with character offset output, large abbreviation tables and CMC support.</description>