Update compiling target version (ucloud#89)

Author: wangrzneu

pom.xml

@@ -83,8 +83,8 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>1.7</maven.compiler.source>
-        <maven.compiler.target>1.7</maven.compiler.target>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
         <junit.version>4.11</junit.version>
         <httpclient.version>4.5.6</httpclient.version>
         <httpmime.version>4.5.6</httpmime.version>