Fix clang format (#854)

Fix invocation of clang-format in CMakeLists and apply clang-format.

src/contrib/graphbuilder.cpp

@@ -14,4 +14,4 @@ void* BuildGraphOfNextDocument(Parser& parser,
     return nullptr;
   }
 }
-}
+}  // namespace YAML

src/contrib/graphbuilderadapter.cpp

@@ -91,4 +91,4 @@ void GraphBuilderAdapter::DispositionNode(void *pNode) {
     m_builder.AppendToSequence(pContainer, pNode);
   }
 }
-}
+}  // namespace YAML