Bump Maven dependencies and plugins

pom.xml

@@ -10,7 +10,7 @@
 		<org.springframework-version>4.2.0.RELEASE</org.springframework-version>
 		<org.springframework.security-version>4.0.2.RELEASE</org.springframework.security-version>
 		<org.springframework.integration-mail-version>4.1.6.RELEASE</org.springframework.integration-mail-version>
-		<com.fasterxml.jackson-version>2.5.4</com.fasterxml.jackson-version>
+		<com.fasterxml.jackson-version>2.6.0</com.fasterxml.jackson-version>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.url>https://scm.thm.de/arsnova</project.url>
 		<sonar.language>java</sonar.language>
@@ -329,7 +329,7 @@
 			<plugin>
 				<groupId>org.eclipse.jetty</groupId>
 				<artifactId>jetty-maven-plugin</artifactId>
-				<version>9.2.11.v20150529</version>
+				<version>9.2.13.v20150730</version>
 				<configuration>
 					<scanIntervalSeconds>1</scanIntervalSeconds>
 					<webApp>
@@ -393,7 +393,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-checkstyle-plugin</artifactId>
-				<version>2.15</version>
+				<version>2.16</version>
 				<configuration>
 					<configLocation>ARSnova-checkstyle-checker.xml</configLocation>
 				</configuration>