attempted FIX:

COSMITS
ENH+FIX: truely delayed SSP

ENH: drop _apply_preprocessing private function

COSMITS
ENH: hide delayed preprocessing
COSMITS
ENH: preallocate where neccessary.
ENH: empty_like
ENHL add missing test
Merge pull request #606 from dengemann/fix_delayed_ssp

FIX: repair lazy ssp projection for Epochs when preload is True