Pass some context to user-supplied interrupt callback

[randomir]

Currently, the interrupt callback function is called after each sample (read), but it receives no context, like last sample or energy. Furthermore, it's not even possible to capture references to sample/energy arrays in closure because they are created in cython code and returned to python on the very end of sampling (i.e. after interrupted).

So, providing references to sample/energy numpy arrays (semi-filled) on each call of interrupt callback would enable user to stop sampling when energy threshold is reached, for example.