Up and download folders are undefined by default

Allow setting a custom Guzzle HTTP Client for requests.

Update README.md

Update DB.php

Fix 'SQLSTATE[HY093]: Invalid parameter number' PDO error which caused of multiple parameters usage in one query.

Send a document as content data using Psr7 stream.

Add note about important changes and update changelog for version 0.44.0.

Update changelog.

Some tiny code fixes.

[skip ci]

Boost deps

Another small additions and changes