merge dev into master

"mageck mle --day0-label" support in Snakefile

revise config.yaml

fix a bug of --trim5 AUTO

adding support for specifying negative control sgRNAs

fix a bug in determining normalization methods

adding examples of negative control sgRNAs in the config.yaml

remove "touch designmatrix" from cli.py

add support for day0label and design matrix

update config.yaml

add mle multi-thread support in config.yaml and Snakefile