Support work in Promise way

[onikienko]

[mattb290]

support async/await

[marios88]

A quick way to do it for now

function bzip(path,path_bz2) {
    return new Promise(function (fulfilled, rejected) {
        _7z.pack(path, path_bz2, function (err) {
            fulfilled(1);
        });
    });
}

async function run() {
    const path = 'file.txt';
    const path_bz2 = 'file.txt.bz2';
    await bzip(path,path_bz2);
}