add nowhere matcher

lib/transition_through/matcher.rb

@@ -61,12 +61,16 @@ def matches?(expect_block)
       @actual_states == @expected_states
     end
 
+    # assert state changes across array or range of values
     def through(*values)
       @expected_states = values.flatten(1)
 
-      self
+      self # allow chaining
     end
 
+    # noop because no change is default assertion
+    def nowhere = self
+
     def failure_message
       "expected block to transition through #{@expected_states.inspect} but it transitioned through #{@actual_states.inspect}"
     end

spec/transition_through_spec.rb

@@ -75,6 +75,14 @@ def decrement(n = 1, by: 1) = n.times { self.count += by }
       expect { counter.increment(3) }.to transition { counter.count }.through 0..3
     end
 
+    it 'should support nothing' do
+      expect { }.to transition { counter.count }
+    end
+
+    it 'should support nowhere' do
+      expect { }.to transition { counter.count }.nowhere
+    end
+
     it 'should track transitions' do
       expect {
         counter.count  = 0