implement DynamicJump for Arm

which is in fact the same as return (moving address into pc)

test/arm/test_translator.rb

@@ -0,0 +1,17 @@
+require_relative 'helper'
+
+module Arm
+  class TestStack < MiniTest::Test
+
+    def test_init
+      assert Translator.new
+    end
+
+    def test_dynamic
+      trans = Translator.new
+      jump = Risc::DynamicJump.new("" , :r1)
+      res = trans.translate jump
+      assert :r1 , res.from
+    end
+  end
+end