ENH Var:  add .argmax(). .argmin(). .argsort()
ENH MneExperiment:  _process_subject_arg() to unify combined group/subject argument
ENH fmtxt HTML:  for Report, allow a site_title different from title
ENH Dataset:  add caption
ENH MneExperiment.show_subjects():  return Dataset
FIX Celltable:  only include non-empty cells to determine within (repeated measure status)
DOC:  testnd.ttest_rel() error message
ENH MneExperiment:  gather ._values from all base classes
RM MneExperiment:  ttests and rm_fake_mris()
ENH MneExperiment:  results file structure
WIP MneExperiment:  PySurfer handling
WIP plot.brain:  use PySurfer Brain as top level