On error, send XML response not just HTTP code

[JustinKyleJames]

When errors are encountered, send the XML response as described here:

https://docs.aws.amazon.com/AmazonS3/latest/API/ErrorResponses.html

Currently we are only sending the HTTP code (404, 500, etc.). This seems to be sufficient with clients but we should be sending the full xml response with more descriptive information.

[korydraughn]

I'm thinking this is 0.3.0.

@JustinKyleJames Thoughts?

[trel]

makes sense. 0.2.0 for immediate needs/functionality.