Update depedencies

Author: Irene

pom.xml

@@ -9,7 +9,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
-        <powermock.version>1.6.2</powermock.version>
+        <powermock.version>1.7.3</powermock.version>
     </properties>
 
     <repositories>
@@ -46,18 +46,18 @@
         <dependency>
             <groupId>com.google.code.gson</groupId>
             <artifactId>gson</artifactId>
-            <version>2.6.2</version>
+            <version>2.8.2</version>
             <scope>compile</scope>
         </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-api</artifactId>
-            <version>1.7.21</version>
+            <version>1.7.25</version>
         </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-log4j12</artifactId>
-            <version>1.7.21</version>
+            <version>1.7.25</version>
         </dependency>
         <dependency>
             <groupId>org.mockito</groupId>