Hotfix: Set customer error_handler only if there is an $app['logger']
Add bytesTo($bytes, $unit, $format)

Samples:
StringUtils::bytesTo(10 * 1024 * 1024, 'GB', '%size%%unit%') return
0.01GB
StringUtils::bytesTo(10 * 1024 * 1024 * 1024, 'GB', '%size%%unit%')
return 10GB
StringUtils::bytesTo(10 * 1024 * 1024 * 1024, 'MB', '%size%%unit%')
return 10240MB
StringUtils::bytesTo(10 * 1024 * 1024 * 1024, 'KB', '%size%%unit%')
return 10485760KB
StringUtils::bytesTo(10 * 1024 * 1024 * 1024, 'B', '%size%:%unit%')
return 10737418240:B