Allow filesystem to be changed on config

Allow to change the filesystem storage on the fly.
For example, you can swap the storage disk with a fake one with
Storage::fake for tests.

this PR goes along with https://github.com/laravel/framework/pull/18860

Updated changelog

Ignore the npm debug log

When an NPM run fails, is created a npm-debug.log file. This file can be ignored and should not be published on a Git based repository.

More clear way to assign middleware in controller

Assign guest middleware to LoginController using documented way https://laravel.com/docs/5.4/controllers#controller-middleware 
to avoid confusing with $options array values meaning.

Add string to validation

Add to axios defaults instead of overwriting them

This change ensures the default "Accept" header specified by axios is retained.

Sorting gitignore file

Make app name configurable in environment file

DRY some npm scripts

`dev` and `prod` are just aliases, so this allows to just defer them to their counterparts.

`watch-poll` just adds one extra argument so the special option `--` allows to pass it to the `watch` script.

NPM scripts should support Windows

Provide consistency with NPM scripts

Add vagrant virtual machine directory to git ignore list.

It trips me up each time that `npm run dev` exists but `npm run prod`
does not. This serves to fix that case, as well as providing consistency
in both directions `dev`/`development` and `prod`/`production`.

[Source](https://twitter.com/michaeldyrynda/status/846507021251690497)

Added changelog

Composer -o

Composer allows us to optimize the autoloader using the --optimize flag or shortly -o.

Require laravel-mix v0.*

Possible URL fix?