use factory to generte intergers in space

start with just integer factory in space
change all the hand-out code
still #14

test/risc/test_register_value.rb

@@ -81,7 +81,7 @@ module Risc
       assert_equal SlotToReg , instr.class
       assert_equal @r1 , instr.array
       assert_equal @r0 , instr.register
-      assert_equal 3 , instr.index
+      assert_equal 4 , instr.index
     end
     def test_reg_to_byte
       instr = @r1[1] <= @r0
@@ -95,7 +95,7 @@ module Risc
       assert_equal RegToSlot , instr.class
       assert_equal @r1 , instr.array
       assert_equal @r0 , instr.register
-      assert_equal 3 , instr.index
+      assert_equal 4 , instr.index
     end
   end
 end