Cf basic object upload

This is a first crack at basic object uploading. A few things to note:

1) I'm using *bytes.Buffer for the BasicUploader and inheriting its methods
2) Instead of implementing the Seeker interface, I used the WriteAt method. Is that sufficient? We can use a Seek method instead (I originally wrote one), but it isn't very efficient to use with a buffer, and we'd have to keep an offset pointer to where the next byte will be written in the buffer.
3) I wrote a test for uploading an object, but it was failing due to the container not being empty, so I created a DeleteObject method. That name and/or method will probably change since, large objects (with manifest files) will need to be handled differently.

Review and feedback desired.