Upgrade to Spring Batch 4.3.9 (#120)

* Upgrade to Spring Batch 4.3.8.

Author: mdeinum

spring-batch-excel/pom.xml

@@ -44,7 +44,7 @@
 
         <java.version>1.8</java.version>
 
-        <spring.batch.version>4.3.7</spring.batch.version>
+        <spring.batch.version>4.3.9</spring.batch.version>
         <poi.version>4.1.2</poi.version>
 
 		<!-- Test Dependencies -->