(ISSUE-99) Upgrade to Java 8

Author: chtyim

pom.xml

@@ -145,8 +145,8 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.1</version>
         <configuration>
-          <source>1.7</source>
-          <target>1.7</target>
+          <source>1.8</source>
+          <target>1.8</target>
           <compilerArgs>
             <arg>-Xlint</arg>
           </compilerArgs>