Upgrade to MyBatis 3.4.4

Fix gh-154

Author: kazuki43zoo

pom.xml

@@ -67,7 +67,7 @@
   </distributionManagement>
 
   <properties>
-    <mybatis.version>3.4.2</mybatis.version>
+    <mybatis.version>3.4.4</mybatis.version>
     <mybatis-spring.version>1.3.1</mybatis-spring.version>
     <spring-boot.version>1.4.5.RELEASE</spring-boot.version>
   </properties>