s3fs 8.x-2.0-alpha1

Issue #2771979 by minakshiPh, chrowe, jansete, naveenvalecha: Update Readme.txt instructions for drupal 8
Issue #2854321 by jansete: Move _s3fs_convert_metadata to S3fsStream class
Issue #2854304 by jansete: Replace deprecated methods and functions
Issue #2854294 by jansete: Replace deprecated check_url by UrlHelper::filterBadProtocol()
Issue #2812747 by rhett.prichard, jansete: drush s3fs-copy-local can not find the exception class?
Issue #2854039 by jansete: Replace deprecated drupal_dirname by \Drupal::service('file_system')->dirname()
Issue #2853154 by jansete: Image not rendered after flush image style
Issue #2853863 by jansete: drupal_static wrong use in ValidateService::getAmazonS3Client()
Issue #2844169 by nehakhadke, jansete: Use StringTranslationTrait $this->t() in OOP
Issue #2853865 by jansete: Replace deprecated file_uri_scheme by Drupal::service('file_system')->uriScheme()
Issue #2829858 by jansete, argiope, bkeller, naveenvalecha: Warning: fstat() expects parameter 1 to be resource, null given in Drupal\s3fs\StreamWrapper\S3fsStream->stream_stat()
Issue #2851889 by jansete: Implements public and private custom folder like Drupal 7 version
Issue #2853794 by jansete: Add support for Seoul/ap-northeast-2
Issue #2851885 by jamiehollern, jansete: Config form does not display region "EU - London (eu-west-2)"
Issue #2851907 by jansete: Bad image references when css is minified
Issue #2826460 by jansete, asgorobets: S3FS does not take over public:// correctly
Issue #2851768 by jansete: Change credentials field description in settings form for use $config var
Issue #2851850 by jansete: Remove duplicated dot in menu link description
Issue #2850271 by zaphoyd, jansete: Add support for Ohio/us-east-2 region
Issue #2767315 by id.tarzanych, webankit, naveenvalecha: Code Cleaning and Removing Error
Issue #2782173 by webankit: Add Mumbai in Region List

It's necessary update your database.

This is the last 8.x-2.x release, we will work on 8.x-3.x branch to match with aws sdk version. So 8.x-2.x won't be supported. The change from 8.x-2.x to 8.x-3.x now will be automatically because it's the same base code.