Do not compress backups if config has 'compress: True'.

I need to run bakthat without compression. This code bypasses compression if 'compress: true' is found on the config file.

I didn't write any tests for it, please check that what I'm doing is reasonable. It's not clear what 'outname' and 'backup_data["size"]' are used for, but I added it anyways (you can call it cargo-cult-driven-development).