Accept -l LAYOUT CLI option to set the layout

lib/uh/wm/cli.rb

@@ -63,6 +63,10 @@ module Uh
             require feature
             @env.log "Loaded `#{feature}' ruby feature"
           end
+
+          opts.on '-l', '--layout LAYOUT', 'specify layout' do |layout|
+            @env.layout_class = self.class.const_get layout.to_sym
+          end
         end
       end
     end

lib/uh/wm/env.rb

@@ -12,7 +12,7 @@ module Uh
       def_delegator :@output, :print
 
       attr_reader   :output
-      attr_accessor :verbose, :debug
+      attr_accessor :verbose, :debug, :layout_class
 
       def initialize output
         @output = output