Fixed some bugs and add tests for articles api

Fixed some major problems and upgrade some packages

Instead of the vue-core-image-upload by cropper.js and improve the up…

…load feature

Fixed the problem for creating the tag and the category

Fixed the bug of the table's pagination

Add the config of the mail notification

Fixed the bug of the notification

Delete the jcrop and add the AvatarUpload component

Solve the problem when enter the user's profile page

Upgrade to 'laravel 5.4' and instead of the 'gulp' by 'laravel-mix'