CLI: Always require 'middleman-core/version'

The `init` command will fail if the `VERSION` was not required because
it is needed for the Gemfile generation. Unfortunately this was not
catched by the specs because the specs require the version and the child
process is not correctly reset.

I was not able to change this easily :-(

middleman-core/lib/middleman-core/cli.rb

@@ -25,7 +25,6 @@ module Middleman
 
       desc 'version', 'Show version'
       def version
-        require 'middleman-core/version'
         say "Middleman #{Middleman::VERSION}"
       end
 
@@ -81,6 +80,9 @@ module Middleman
   end
 end
 
+# Require the Middleman version
+require 'middleman-core/version'
+
 # Include the core CLI items
 require 'middleman-core/cli/init'
 require 'middleman-core/cli/bundler'