Use string::compare to improve performance.
Use static_cast instead of reinterpret_cast for hierarchy navigation.
Merge pull request #23 from masamitsu-murase/use_static_cast_for_hierarchy_navigation

Use static_cast instead of reinterpret_cast for hierarchy navigation.
Merge pull request #24 from masamitsu-murase/use_compare

Use string::compare to improve performance.