try to fix travis build error

.travis.yml

@@ -15,8 +15,7 @@ before_install:
   - pip install --user codecov
 
 after_success:
-  - mvn clean cobertura:cobertura coveralls:report
-  - mvn clean site
+  - mvn clean site -DskipTests=true
   - codecov
 
 branches:
@@ -37,3 +36,7 @@ addons:
     build_command_prepend: "mvn clean"
     build_command:   "mvn -DskipTests=true compile"
     branch_pattern: master
+
+cache:
+  directories:
+  - $HOME/.m2

apollo-buildtools/pom.xml

@@ -24,6 +24,7 @@
 		<plugins>
 			<plugin>
 				<artifactId>maven-resources-plugin</artifactId>
+				<version>2.6</version>
 				<executions>
 					<execution>
 						<id>copy-resources</id>

apollo-client/src/test/resources/log4j2.xml

@@ -10,7 +10,7 @@
     </appenders>
     <loggers>
         <logger name="com.ctrip.framework.apollo" additivity="false" level="trace">
-            <AppenderRef ref="Async" level="DEBUG"/>
+            <AppenderRef ref="Async" level="INFO"/>
         </logger>
         <root level="INFO">
             <AppenderRef ref="Async"/>