Bump download-maven-plugin to 1.6.7 (#361)

Https proxy works after 1.5.1. See download-maven-plugin/download-maven-plugin#157

Author: yejianfengblue

install/pom.xml

@@ -13,7 +13,7 @@
       <plugin>
         <groupId>com.googlecode.maven-download-plugin</groupId>
         <artifactId>download-maven-plugin</artifactId>
-        <version>1.3.0</version>
+        <version>1.6.7</version>
         <executions>
           <execution>
             <phase>process-resources</phase>