Add logback-classic as log impl

apollo-common/pom.xml

@@ -31,5 +31,9 @@
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-commons</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>ch.qos.logback</groupId>
+			<artifactId>logback-classic</artifactId>
+		</dependency>
 	</dependencies>
 </project>

pom.xml

@@ -136,6 +136,11 @@
 				<artifactId>guava</artifactId>
 				<version>19.0</version>
 			</dependency>
+			<dependency>
+				<groupId>ch.qos.logback</groupId>
+				<artifactId>logback-classic</artifactId>
+				<version>1.1.7</version>
+			</dependency>
 			<dependency>
 				<groupId>org.eclipse.jetty</groupId>
 				<artifactId>jetty-server</artifactId>