Fixes a bug about potential hash collision in bindings. Using string as key of unordered_map rather than `long` value from `typeid(T).hash_code()`.
Merge pull request #61 from dumganhar/hash_code_fix

Fixes a bug about potential hash collision in bindings. Using string as key of unordered_map rather than `long` value from `typeid(T).hash_code()`.