stop(cwd) {
        const fkill = require('fkill');
        const errors = require('../errors');

        let pid;

        try {
            pid = parseInt(fs.readFileSync(path.join(cwd, PID_FILE)));
        } catch (e) {
            if (e.code === 'ENOENT') {
                // pid was not found, exit
                return Promise.resolve();
            }

            return Promise.reject(new errors.CliError({
                message: 'An unexpected error occurred when reading the pidfile.',
                error: e
            }));
        }

        return fkill(pid, {force: this.system.platform.windows}).catch((error) => {
            // TODO: verify windows outputs same error message as mac/linux
            if (!error.message.match(/No such process/)) {
                return Promise.reject(new errors.CliError({
                    message: 'An unexpected error occurred while stopping Ghost.',
                    err: error
                }));
            }
        }).then(() => {
            fs.removeSync(path.join(cwd, PID_FILE));
        });
    }
Stops an instance

@param {string} cwd Current working directory
@return Promise<void>

@method stop
@public