mirego/MCAWSS3Client — pull request #4 by jayztemplier (2014-02-03 02:38:18+00:00)
Title: add the ability to set some metadata to a request

I followed those instruction to be able to add some metadata in a put request:
http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPUT.html

Example:
```
[client putObjectWithData:imageData key:key mimeType:@"image/jpg" metadata:@{@"body" : @"custom body"} progress:^(NSUInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToWrite) {

} success:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(@"Upload Successful! %@", [operation responseString]);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Upload Failed... %@", error);
}];

```