WIP: ENH:  add `labels_from_clusters()` (NEED proper smooth values)
ENH NDVar:  make boolean NDVar from comparison
OPT plot:  import plot.brain without importing surfer
FIX MneExperiment:  assign `subject` field values `[]` when `find_subjects==False`
ENH Notifier:  Drop into PDB on exception
API Notifier:  remove message stack (simplify)
FIX NDVar:  implement Dimension.__ne__()
WIP:  OPT nd-anova:  preallocate arrays
FIX MneExperiment.plot_annot()
OPT/STY lm_fitter:  precompute effects and dfs
STY LMFitter:  rename lm_fitter -> LMFitter; X-->x
OPT LMFitter:  pre-allocate result when splitting
API LMFitter:  .map() returns list of F-maps
API glm:  capitalization  lm -> LM, anova -> ANOVA
TEST LMFitter