v0.1.0

Refactored all the code using template to support different time unit : Tick, Quarter, Second( not implemented yet)

I put all this template class in symusic.core and for convenience, we define some functions in symusic with multiple overloads for object creating, Like symusic.Note

Now, you can create object by adding time_unit, like Note(1,1,1,1, "quarter") or Note(1,1,1,1, symusic.typing.Tick)

Note that, although it looks like a duck type, there are still some different:

1. Note is a function, but not a class
2. The created object will belong to a class like symusic.core.NoteTick
3. Note in different class (like NoteTick and NoteQuarter) can not be directly converted (we'll design a converting system in the future)