don't error out if no regex was entered

It's a valid use case to run the search function, but abort.
This shouldn't be scolded.
`snotes -s` respects DMENU_ARGS
use '/command' instead of ' command'
create config file if does not exist
add DMENU_ARGS example in config
add color parameter to DMENU_ARGS example
die if we don't have an argument for the command
check if the file exist in 'blame' and 'changed'
stick to '|| die' scheme