Avoid deprecation warning
Remove extra comma
AWS no longer escapes forward slash in the identifier
Use AWS subdomain when possible. Copied from CarrierWave 0.8.0
Implement #url as #public_url
Create an authenticated URL when needed. Copied from CarrierWave 0.8.0
Write in binary file mode
Merge branches 'minor_changes', 'authentication' and 'write_binary_file'