add a cli command line

Usage: localenv [envFile] -- <command> [commandArgs ...]

Options:

    -h, --help     output usage information
    -V, --version  output the version number

localenv command line will load any command with
localenv computed process.env

You can either pass a custom .env file or rely on the default .env file
if any.
pin commander dependency
Merge pull request #2 from vvo/localenv-cli

add a cli command line
History: update
v0.2.0
kill child when SIGTERM/SIGINT

we must manually forward SIGTERM/SIGINT to
the child when localenv cli receives theses events

So that there's no zombie process
Merge pull request #3 from vvo/cli-kill-child-when-sigterm

kill child when SIGTERM/SIGINT
update history
v0.2.1