Add cuke for be_kind_of and be_instance_of matchers.

- Closes #31.

features/matchers/types.feature

@@ -0,0 +1,115 @@
+Feature: Type Check matchers
+
+  rspec-expectations includes two matchers to assist you with
+  checking the types of your objects:
+
+    * obj.should be_kind_of(type): calls obj.kind_of?(type), which returns
+      true if type is in obj's class hierarchy or is a module and is
+      included in a class in obj's class hierarchy.
+    * obj.should be_instance_of(type): calls obj.instance_of?(type), which
+      returns true if and only if type if obj's class.
+
+  Both of these matchers have aliases:
+
+    * obj.should be_a_kind_of(type) # same as obj.should be_kind_of(type)
+    * obj.should be_a(type) # same as obj.should be_kind_of(type)
+    * obj.should be_an(type) # same as obj.should be_kind_of(type)
+    * obj.should be_an_instance_of(type) # same as obj.should be_instance_of(type)
+
+  Scenario: be_(a_)kind_of matcher
+    Given a file named "be_kind_of_matcher_spec.rb" with:
+      """
+      module MyModule; end
+
+      class Fixnum
+        include MyModule
+      end
+
+      describe 17 do
+        # the actual class
+        it { should be_kind_of(Fixnum) }
+        it { should be_a_kind_of(Fixnum) }
+        it { should be_a(Fixnum) }
+
+        # the superclass
+        it { should be_kind_of(Integer) }
+        it { should be_a_kind_of(Integer) }
+        it { should be_an(Integer) }
+
+        # an included module
+        it { should be_kind_of(MyModule) }
+        it { should be_a_kind_of(MyModule) }
+        it { should be_a(MyModule) }
+
+        # negative passing case
+        it { should_not be_kind_of(String) }
+        it { should_not be_a_kind_of(String) }
+        it { should_not be_a(String) }
+
+        # deliberate failures
+        it { should_not be_kind_of(Fixnum) }
+        it { should_not be_a_kind_of(Fixnum) }
+        it { should_not be_a(Fixnum) }
+        it { should_not be_kind_of(Integer) }
+        it { should_not be_a_kind_of(Integer) }
+        it { should_not be_an(Integer) }
+        it { should_not be_kind_of(MyModule) }
+        it { should_not be_a_kind_of(MyModule) }
+        it { should_not be_a(MyModule) }
+        it { should be_kind_of(String) }
+        it { should be_a_kind_of(String) }
+        it { should be_a(String) }
+      end
+      """
+    When I run "rspec be_kind_of_matcher_spec.rb"
+    Then the output should contain all of these:
+      | 24 examples, 12 failures                 |
+      | expected 17 not to be a kind of Fixnum   |
+      | expected 17 not to be a kind of Integer  |
+      | expected 17 not to be a kind of MyModule |
+      | expected 17 to be a kind of String       |
+
+  Scenario: be_(an_)instance_of matcher
+    Given a file named "be_instance_of_matcher_spec.rb" with:
+      """
+      module MyModule; end
+
+      class Fixnum
+        include MyModule
+      end
+
+      describe 17 do
+        # the actual class
+        it { should be_instance_of(Fixnum) }
+        it { should be_an_instance_of(Fixnum) }
+
+        # the superclass
+        it { should_not be_instance_of(Integer) }
+        it { should_not be_an_instance_of(Integer) }
+
+        # an included module
+        it { should_not be_instance_of(MyModule) }
+        it { should_not be_an_instance_of(MyModule) }
+
+        # another class with no relation to the subject's hierarchy
+        it { should_not be_instance_of(String) }
+        it { should_not be_an_instance_of(String) }
+
+        # deliberate failures
+        it { should_not be_instance_of(Fixnum) }
+        it { should_not be_an_instance_of(Fixnum) }
+        it { should be_instance_of(Integer) }
+        it { should be_an_instance_of(Integer) }
+        it { should be_instance_of(MyModule) }
+        it { should be_an_instance_of(MyModule) }
+        it { should be_instance_of(String) }
+        it { should be_an_instance_of(String) }
+      end
+      """
+    When I run "rspec be_instance_of_matcher_spec.rb"
+    Then the output should contain all of these:
+      | 16 examples, 8 failures                     |
+      | expected 17 not to be an instance of Fixnum |
+      | expected 17 to be an instance of Integer    |
+      | expected 17 to be an instance of MyModule   |
+      | expected 17 to be an instance of String     |