updated minimum pandas version due to deprecated diff function
updated minimum pandas version due to deprecated diff function

AZMAG/urbansim,UDST/urbansim,apdjustino/urbansim,synthicity/urbansim,AZMAG/urbansim,AZMAG/urbansim,AZMAG/urbansim,synthicity/urbansim,apdjustino/urbansim,synthicity/urbansim,UDST/urbansim,UDST/urbansim,synthicity/urbansim,UDST/urbansim,apdjustino/urbansim,apdjustino/urbansim