'list_parts' and a test for s3 multipart uploads

[marios]

Hi Travis - as promised here's a test for the multipart S3 uploads stuff. Includes a couple fixes I found along the way and I also added the 'list_parts' method docs here

For the test you need to add the location of 2 files (which must be > 5mb for multipart to work) to your aws.yml file... like:

1 ---$
2 amazon:$
3   access_key: "KEY"$
4   secret_key: "PASS"$
5   my_prefix: "mariosFoo"$
6   multipart_segment1: "/home/marios/Downloads/blob1.txt"$
7   multipart_segment2: "/home/marios/Downloads/blob2.txt"$

The test exercises initiating, uploading both parts, listing parts and then completing the upload... so may take some time depending on your bandwidth and the size of the parts you specify (must be >5mb - dictated by S3 API).

thanks! marios