Bump junit from 4.12 to 4.13.1 in /japanese-addon (#11)

diff --git a/japanese-addon/pom.xml b/japanese-addon/pom.xml
index 8ceff3e..36ac3d1 100644
--- a/japanese-addon/pom.xml
+++ b/japanese-addon/pom.xml
@@ -18,7 +18,7 @@
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>4.12</version>
+      <version>4.13.1</version>
       <scope>test</scope>
     </dependency>