Make errmsg part of module

[toymachiner62]

I see you have this nice function below which displays the actual error message. You should make this part of this package so that everyone doesn't have to manually implement this method.

function errmsg(err) {
    var str = 'Error: '
    // if it's a libuv error then get the description from errno
    if (errno.errno[err.errno]) {
        str += errno.errno[err.errno].description
    } else {
        str += err.message
    }

    // if it's a `fs` error then it'll have a 'path' property
    if (err.path) {
        str += ' [' + err.path + ']'
    }
    return str
}