Change source level from 1.7 to 1.8

Author: junichi11

pom.xml

@@ -26,8 +26,8 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>2.5.1</version>
                 <configuration>
-                    <source>1.7</source>
-                    <target>1.7</target>
+                    <source>1.8</source>
+                    <target>1.8</target>
                 </configuration>
             </plugin>
             <plugin>