Added a spec for CharSet#include?.

spec/char_set_spec.rb

@@ -49,12 +49,22 @@
     end
   end
 
-  it "should include Strings" do
-    @char_set.include_char?('A').should == true
+  it "should include characters" do
+    @char_set.include_char?('A').should be_true
   end
 
-  it "should include Integers" do
-    @char_set.should include(0x41)
+  it "should include bytes" do
+    @char_set.include_byte?(0x41).should be_true
+  end
+
+  describe "#include?" do
+    it "should accept characters" do
+      @char_set.should include('A')
+    end
+
+    it "should accept bytes" do
+      @char_set.should include(0x41)
+    end
   end
 
   it "should be able to select bytes" do