Add Disqus, Google Analytics and support for Menu Templates

[bhavin192]

• Add Google Analytics support
  • This is disabled if user doesn't provide googleAnalytics in config
• Add Disqus support
  • This is disabled if user doesn't provide disqusShortname in config
• Show .Site.Params.description in sidebar if set
• Show GitHub details only if .Site.Params.Github is set
• Add support for Menus (keeping the sidebar: true implementation for backward compatibility)
  • https://gohugo.io/content-management/menus/

Should I add an example to the example site about using the Menus in front matter or in configuration?

[tummychow]

Should I add an example to the example site about using the Menus in front matter or in configuration?

sure, i'll accept a PR for this if you have one