rcond=-1 Addition to surpress FutureWarning

[jwbishop]

FutureWarning: rcond parameter will change to the default of machine precision times max(M, N) where M and N are the input matrix dimensions.
To use the future default and silence this warning we advise to pass rcond=None, to keep using the old, explicitly pass rcond=-1. c500 = np.linalg.lstsq(X_500, y_500)[0]

This issue is known, and appears to be harmless.
scikit-learn-contrib/py-earth#194