NF: support for gifti I/O through nibabel.gifti. XXX the surf_gifti.write function has two hacks to ensure that files are written properly - may require some refactoring in nibabel.gifti
ENH: make overwriting spec files the default
BF: ensure that written coordinates in gifti are float32 / int32 irrespective of surface arrays
ENH: by default add node indices to gifti surfaces