V3.0.0: Full PHP 7.1+ code rewriting

Rewrite using PHP 7.1 syntax

V1.1.2

PHP 7.2 Yii compliance

V1.1.1

Simple bugfix on disconnect

V1.1

New functionnality

• Issue #2 Add SftpDriver::fileExists method for testing remote file/folder existence

V1.0

SFTP drivers for (hguenot/yii2-gftp) [https://github.com/hguenot/yii2-gftp] extensions