Updated pom.xml to depend on mesos 0.20.0.

Author: vinodkone

pom.xml

@@ -73,7 +73,7 @@
       <dependency>
           <groupId>org.apache.mesos</groupId>
           <artifactId>mesos</artifactId>
-          <version>0.19.0</version>
+          <version>0.20.0</version>
       </dependency>
       <dependency>
           <groupId>com.google.protobuf</groupId>