WG-NOTE does not generate Previous version header

[fhirsch]

Generating a WG-NOTE does not include a previous version header. It should, for example when previousPublishDate and previousMaturity are set.

This works fine for specStatus WD but fails for specStatus WG-NOTE

[marcoscaceres]

This WFM. Tested using:

      var respecConfig = {
        specStatus: "WG-Note",
        editors: [{
          name: "Your Name",
          url: "http://your-site.com",
        }],
        processVersion: 2015,
        edDraftURI: "http://some.github.repo",
        shortName: "dahut",
        previousMaturity: "WD",
        previousPublishDate: "2014-12-12", 
      };

And seen output: