More missing implicit conversions

[Maxwell175]

Here are a few more implicit conversions I noticed are missing:

Tuple[float, float, float] > Vec3

Tuple[float, float, float, float] > Vec4

Coroutine > AsyncTask

[WMOkiishi]

I'll look into adding these once I've finished reworking the existing coercion logic. (It turns out it wasn't quite aligned with the runtime behavior.)

I've been hesitant to add support for coercion of tuples to vectors, but I think adding it is probably the right thing to do.

I don't see a constructor for converting a Coroutine to an AsyncTask. Do you have any more information?