Possibly deal with a good chunk of the old_divs

SimPEG/MT/Problem1D/Probs.py

@@ -4,7 +4,6 @@ from __future__ import unicode_literals
 from __future__ import absolute_import
 from future import standard_library
 standard_library.install_aliases()
-from past.utils import old_div
 from SimPEG.EM.Utils import omega
 from SimPEG import mkvc
 from scipy.constants import mu_0