isRunning(cwd) {
        const isRunning = require('is-running');

        const pidfile = path.join(cwd, PID_FILE);

        if (!fs.existsSync(pidfile)) {
            // Even if the process exists, if the file has been deleted we really can't
            // determine if it's still running, so just assume it's not.
            return false;
        }

        const pid = parseInt(fs.readFileSync(pidfile));
        const running = isRunning(pid);

        if (!running) {
            // If not running, cleanup the pid file
            fs.removeSync(pidfile);
        }

        return running;
    }
Checks if the Ghost instance is running

@param {string} cwd
@return bool Whether or not the process is still running

@method isRunning
@public