add TSamLast command for reexecuting last running tests

tests/test_samurai_output_spec.lua

@@ -61,4 +61,19 @@ describe("test-samurai public API", function()
 
     assert.is_true(called)
   end)
+
+  it("delegates test_last to core.run_last", function()
+    local called = false
+    local orig = core.run_last
+
+    core.run_last = function()
+      called = true
+    end
+
+    test_samurai.test_last()
+
+    core.run_last = orig
+
+    assert.is_true(called)
+  end)
 end)