Merge pull request mattn#37 from mattn/fix-36

Fix mattn#36

Merge pull request mattn#35 from markus-oberhumer/minor-testcase-clea…

…nups

Minor testcase cleanups

Revert change of go.mod

Add test

Merge pull request mattn#31 from marckhouzam/fix/emptyArg

Support empty arguments

Do not specify version

Merge pull request mattn#23 from mattn/dollar-fix

Handle FOO=$(command)

Merge pull request mattn#22 from radeksimko/go-mod

Enable go modules

update README.md

fix emtpy arguments

fixes mattn#5