close #21

Mostly replaced Fixnum with integer
also in the rx-file dependency
all travis and testing with 2.4+

test/risc/interpreter/calling/test_alloc.rb

@@ -51,7 +51,7 @@ module Risc
       assert_equal :- , op.operator
       assert_equal :r3 , op.left.symbol
       assert_equal :r1 , op.right.symbol
-      assert_equal Fixnum , @interpreter.get_register(:r3).class
+      assert_equal ::Integer , @interpreter.get_register(:r3).class
       assert 0 != @interpreter.get_register(:r3)
     end
     def test_branch

test/risc/interpreter/calling/test_div10.rb

@@ -47,7 +47,7 @@ module Risc
       ret = main_ticks(93)
       assert_equal FunctionReturn ,  ret.class
       link = @interpreter.get_register( ret.register )
-      assert_equal Fixnum , link.class
+      assert_equal ::Integer , link.class
     end
   end
 end