add a test for -limit functionality

propagate error exit status of called process

README: mention new -count option

relicense as MIT

bump version to 1.3.1

add new -count option

fix new command line parser for -j

add new linenumber substitution feature

fix typo in --help output

add some argument permutation tests

README: fix markdown

bump version to 1.3.0

Makefile: add check target

fix test.sh

make all funcs static