remove unbundled extensions from default config

middleman-core/lib/middleman-core/templates/shared/config.tt

@@ -2,10 +2,6 @@
 # Compass
 ###
 
-# Susy grids in Compass
-# First: gem install susy
-# require 'susy'
-
 # Change Compass configuration
 # compass_config do |config|
 #   config.output_style = :compact
@@ -82,11 +78,6 @@ configure :build do
   # Use relative URLs
   # activate :relative_assets
 
-  # Compress PNGs after build
-  # First: gem install middleman-smusher
-  # require "middleman-smusher"
-  # activate :smusher
-
   # Or use a different image path
   # set :http_path, "/Content/images/"
 end