Removed `lib/middleman_extension.rb', I understand this was a 'hack' in version 2.x before the newer extension API was available.
Removed `lib/middleman_extension.rb', I understand this was a 'hack' in version 2.x before the newer extension API was available.

Will migrate to new extension API.

simonrice/middleman-disqus,simonrice/middleman-disqus