Use newer AWS SDK that correctly handles buckets in different regions

Right now, the plugin dies horribly if your bucket is in an unexpected region.

This is what's happening (via curl):

```
> GET /BUCKET-NAME HTTP/1.1
> User-Agent: curl/7.24.0 (x86_64-apple-darwin12.0) libcurl/7.24.0 OpenSSL/0.9.8r zlib/1.2.5
> Host: s3.amazonaws.com
> Accept: */*
>
< HTTP/1.1 301 Moved Permanently
< x-amz-request-id: D75BAD9E2517644B
< x-amz-id-2: drlAYrg34WM1pgL2sRZE7VHLNqdXV7JUHx9QOD5BY+V2DRugkaJE4RBiOPGOHvHx
< Content-Type: application/xml
< Transfer-Encoding: chunked
< Date: Thu, 18 Apr 2013 20:15:24 GMT
< Server: AmazonS3
<
<?xml version="1.0" encoding="UTF-8"?>
* Connection #0 to host s3.amazonaws.com left intact
<Error><Code>PermanentRedirect</Code><Message>The bucket you are attempting to access must be addressed using the specified endpoint. Please send all future requests to this endpoint.</Message><RequestId>D75BAD9E2517644B</RequestId><Bucket>BUCKET-NAME</Bucket><HostId>drlAYrg34WM1pgL2sRZE7VHLNqdXV7JUHx9QOD5BY+V2DRugkaJE4RBiOPGOHvHx</HostId><Endpoint>BUCKET-NAME.s3.amazonaws.com</Endpoint></Error>
```

The older version of the AWS SDK does not correctly handle this response, so the upload fails with:

```
Could not connect to repository: Unable to execute HTTP request: null: ClientProtocolException: Received redirect response HTTP/1.1 301 Moved Permanently but no location header
```

Switching to use an up-to-date version of the SDK solves this.