Usage:
    $ if-node-version <VersionRange> <Command> [...args]

        Run a shell command if it's on the node of specified versions.
        Otherwise, do nothing.

        Exit code is the exit code of the <Command>.

    $ if-node-version <VersionRange>

        Check if it's on the node of specified versions.

        Exit code is 0 if it's on the node of specified versions.
        Otherwise, exit code is 1.

    $ if-node-version --help

        Show this help text.

    $ if-node-version --version

        Show the version number of `if-node-version` command.

Parameters:
    <VersionRange> .... A text which specifies the version range of Node.js
                        This text format is defined by node-semver module:
                        https://www.npmjs.com/package/semver#ranges
    <Command> ......... A shell command.
    [...args] ......... Parameters of the shell command.

Examples:
    $ if-node-version ">=4" eslint lib test
    $ if-node-version "<6" node ./scripts/fallback.js