fix small typos in tests
avoid time and memory intensive merge operation
gt chunks are compressed on the fly

before hitting the disk
rm debug statements
shorten 'zip' cis splitting option
cis spitting script is less verbose
cis-spitting scripts reads gex data file once only

so e.g. it can be coming from a pipe
add 'cis data preparation pipeline' script to repo

takes typical cis-eqtl data in input, produces preset chunks folders+data in output