update test libraries (#26)

diff --git a/pom.xml b/pom.xml
index b8ec790..53c1f89 100644
--- a/pom.xml
+++ b/pom.xml
@@ -222,19 +222,19 @@
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>4.12</version>
+      <version>4.13</version>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.hamcrest</groupId>
       <artifactId>hamcrest-core</artifactId>
-      <version>1.3</version>
+      <version>2.2</version>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.hamcrest</groupId>
       <artifactId>hamcrest-library</artifactId>
-      <version>1.3</version>
+      <version>2.2</version>
       <scope>test</scope>
     </dependency>
     <dependency>