Apply suggestions from code review

Author: jeremylong

pom.xml

@@ -188,9 +188,9 @@ Copyright (c) 2012 - Jeremy Long
         <pluginManagement>
             <plugins>
                 <plugin>
-                    <groupId>org.codehaus.mojo</groupId>
-                    <artifactId>exec-maven-plugin</artifactId>
-                    <version>3.6.2</version>
+                    <groupId>com.googlecode.maven-download-plugin</groupId>
+                    <artifactId>download-maven-plugin</artifactId>
+                    <version>1.13.0</version>
                 </plugin>
                 <plugin>
                     <groupId>org.jsonschema2pojo</groupId>