Update to make plugin work with GoCD 17.1 and above

[arvindsv]

Using the plugin shim to upgrade this plugin, so that it works with 17.1. Without this change, this plugin will stop working from GoCD 17.1 onwards.

[arvindsv]

The configuration I used to verify this change is:

<repository id="bff28240-9028-4a85-a2f0-322bc0d06cd8" name="puppet-test">
  <pluginConfiguration id="puppetforge" version="1" />
  <configuration>
    <property>
      <key>FORGE_URL</key>
      <value>https://forge.puppet.com</value>
    </property>
  </configuration>
  <packages>
    <package id="5532775c-b9a2-473c-bb04-54008612e627" name="test-pkg">
      <configuration>
        <property>
          <key>MODULE_NAME</key>
          <value>puppetlabs/azure</value>
        </property>
      </configuration>
    </package>
  </packages>
</repository>

[arvindsv]

Hmm. The build failed, because download-dependencies.rb does not exist any more. The travis YML has to change.