rename risc_value to register_value

almost to register, but it still carries that value

lib/risc/instructions/getter.rb

@@ -23,9 +23,9 @@ module Risc
       @index = index
       @register = register
       raise "index #{index}" if index.is_a?(Numeric) and index < 0
-      raise "Not integer or reg #{index}" unless index.is_a?(Numeric) or RiscValue.look_like_reg(index)
-      raise "Not register #{register}" unless RiscValue.look_like_reg(register)
-      raise "Not register #{array}" unless RiscValue.look_like_reg(array)
+      raise "Not integer or reg #{index}" unless index.is_a?(Numeric) or RegisterValue.look_like_reg(index)
+      raise "Not register #{register}" unless RegisterValue.look_like_reg(register)
+      raise "Not register #{array}" unless RegisterValue.look_like_reg(array)
     end
     attr_accessor :array , :index , :register