Implement Disqus comments

[vkurup]

• Add ':' between meta_title and site_title in base.html template
• Add DISQUS_HOSTNAME and DISQUS_SHORTNAME to settings
• Add Disqus div and JS to project-detail page
• Document settings in Developer docs

[calebsmith]

I have one small inline comment that should be addressed or discussed. Otherwise :dango:

I look forward to commenting on projects and seeing others do the same.