[boost] [type_traits] type_traits for types with operator().

Hello. Recently I looked for type_traits for callable classes. It so strange, I didn't find such traits. Most likely, I just missed them or something like them. I actually don't know is there a real need for them. Anyway I tried to write such traits at least for practice and metaprogramming training. I tested them with gcc, clang and msvc2010. I would appreciate if you looked at the code. Here is the linkhttps://github.com/AntonBikineev/is_functional/ to my github repository. It's cool that they can see hidden generated operator() of lambdas closure type. Best regards, Anton.