eGRF speedup with Pythran

[MuellerSeb]

The laplace solution of the eGRF Model could use a speedup and Pythran looks promising for this task.

This routine takes a lot of time:

AnaFlow/anaflow/flow/laplace.py

Line 59 in 2a3eb65

def grf_laplace(

This loop should be moved in a Pythran function:

AnaFlow/anaflow/flow/laplace.py

Line 227 in 2a3eb65

for si, se in enumerate(s):

Following the Pythran doc, every needed numpy/scipy routine should be supported.

[MuellerSeb]

Superseded by #15