FIX bug related to loading datablocks.

datablocks can have a length different than the sampling frequency. The current code assumes that the sampling frequency and the number of samples per block are the same. This turns out to be a bad assumption.
FIX indexing error.

chan_data is 1d so the index should be 0.
FIX stim channel interpolation
ADD padding and PEP8
Merge pull request #1574 from t3on/tb-edf-FIX

FIX bug related to loading datablocks.