Add reset method in curb adapter

lib/webmock/http_lib_adapters/curb_adapter.rb

@@ -332,6 +332,11 @@ def on_#{callback} &block
           end
         METHOD
       end
+
+      def reset
+        instance_variable_set(:@body_str, nil)
+        super
+      end
     end
   end
 end

spec/acceptance/curb/curb_spec.rb

@@ -462,5 +462,20 @@
       it_should_behave_like "Curb"
       include CurbSpecHelper::ClassPerform
     end
+
+    describe "using .reset" do
+      before do
+        @curl = Curl::Easy.new
+        @curl.url = "http://example.com"
+        body = "on_success fired"
+        stub_request(:any, "example.com").to_return(body: body)
+        @curl.http_get
+      end
+
+      it "should clear the body_str" do
+        @curl.reset
+        expect(@curl.body_str).to eq(nil)
+      end
+    end
   end
 end