Move scipy imports so that they don't happen on startup.

There seems to be an issue with loading scipy while mantid is
imported in vanilla python. Move the import so that it happens later.
Refs #8373

Code/Mantid/Framework/PythonInterface/plugins/functions/StretchedExpFT.py

@@ -34,8 +34,6 @@
 from mantid.api import IFunction1D, FunctionFactory #, BoundaryConstraint
 from mantid import logger
 import numpy as np
-from scipy.fftpack import fft
-from scipy.interpolate import interp1d
 import copy
 
 from pdb import set_trace as tr
@@ -98,6 +96,9 @@ def function1D(self, xvals, **optparms):
         an extra factor exp(i*pi*E/de) which amounts to alternating sign every
         time E increases by de, the energy bin width
         '''
+        from scipy.fftpack import fft
+        from scipy.interpolate import interp1d
+
         p=self.validateParams()
         # override parameter values with optparms (used for the numerical derivative)
         if optparms: