OPT ClusterDist;  API: drop support for tmin criterion (use mintime)
OPT ClusterDist:  pre-allocate memory buffers
ENH ClusterDist:  TFCE (Threshold-free cluster enhancement)
API testnd:  default pmin to None
ENH ClusterDist:  add trends to TFCE table
OPT ClusterDist:  cluster labeling
OPT ClusterDist:  cluster labeling (optimized connectivity representation)
API ClusterDist:  Only store cropped data
API testnd:  RM clean_time_axis()
ENH ClusterDist:  find local maxima
ENH Dataset:  .add_empty_var()
TEST ClusterDist:  TFCE
ENH ClusterDist:  pickle support
ENH ClusterDist:  separate methods for result properties
ENH ClusterDist:  separate method for cluster properties
ENH ClusterDist:  ADD .masked_parameter_map() method
WIP DOC _mne
WIP ClusterDist progress logging
WIP TestResult class
FIX t-contrast:  infer tail from contrast