Added dedicated fps command

lib/ui/commands/fps_command.rb

@@ -0,0 +1,32 @@
+class IMICFPS
+  class Commands
+    class FPSCommand < Command
+      def group
+        :global
+      end
+
+      def command
+        :fps
+      end
+
+      def handle(arguments, console)
+        case arguments.last
+        when "", nil
+          console.stdin("#{Style.highlight("fps")}: #{$debug.get(:fps)}")
+        when "on"
+          var = $debug.set(:fps, true)
+          console.stdin("fps => #{Style.highlight(var)}")
+        when "off"
+          var = $debug.set(:fps, false)
+          console.stdin("fps => #{Style.highlight(var)}")
+        else
+          console.stdin("Invalid argument for #{Style.highlight("#{command}")}, got #{Style.error(arguments.last)} expected #{Style.notice("on")}, or #{Style.notice("off")}.")
+        end
+      end
+
+      def usage
+        "#{Style.highlight("fps")} #{Style.notice("[on|off]")}"
+      end
+    end
+  end
+end