Added the capability in i/o to read the dipole moment from vasprun.xml if it exists

Very minor code changes so that dipole moment can be read from vasprun.xml.

try: lastdipole = step.findall('scstep/dipole')[-1] except: lastdipole = None

dipole = None if lastdipole is not None: dblock = lastdipole.find('v[@name="dipole"]') if dblock is not None: dipole = np.zeros((1,3), dtype=float) dipole = np.array([float(val) for val in dblock.text.split()])