Update communication_channels.rst

bump importRosbag to v1.0.4

Create requirements.txt for Binder

Merge pull request neuromorphs#258 from anindyaghosh/event_downsampling

Event based spatio-temporal downsampling

use numpy struct to unstruct function for timesurface generation

change Timesurface transform parameters and speed it up considerably

update docs notebook with new ToTimesurface transform

update docs gallery script for ToTimesurface

raise error if single polarity is used for sensor size but data conta…

…ins more than one polarity

make sure librosa.utils.fix_length is calling data, size and axis