Add template_date_format parameter

  Pass it to TemplateCJM as date_format
  Bump version to 4.20
  Require version 4.20 of TemplateCJM (for date_format)
    and Test::PrereqsFromMeta (to ensure Dist-Zilla-Plugins-CJM
    doesn't contain an older TemplateCJM)
Reformat Changes to match spec
Updated Changes for August 24, 2013 release of 4.20