3.0.12/3.1.6

Version 3.0.12/ Androidx version 3.1.6

1. Download TotalBytes fixes. Thanks to @badrazizi
2. OnCompleted not called in some instances.
3. Fixed " A resource failed to call close" errors. Thanks to @Braxeo
4. Fixed Pen Test issues: Thanks to @StuStirling
5. Added new batch enqueue method. Thanks to @thib-rdr
6. Fixed rapid pause and resume issues. Thanks to @jpvs0101
7. Breaking change. Reverted OkHttp client to 3.12.12 to support Android versions older than 21. Thanks to @badrazizi
8. Fixed issues with sample app

Big thanks to everyone who contributed and open issues. Happy Holidays. Stay Safe!