Jupyter integration. Output compiler log, diagnostic info, etc..

[sklam]

There's a open PR in Jupyter, jupyter/jupyter_client#376, that adds support for transient data. In its description, example transient data includes:

1. Status/Progress information. For calculations that take a long time to execute, the kernel might want to send some progress information to the frontend.
2. Debug information. A kernel might want to output more verbose information under certain debug mode. The information can be long and are not meant to be saved with the notebook.
3. Side effect of calculation. In addition to regular result, a kernel might want to output some information about the result. As an extreme example, after the execution of a=1 that does not produce any real output, the kernel might want to display the value of a as a side effect of the calculation.

Numba can print compilation progress, inspection, diagnostic info, etc..