Return correct value for base64 and empty strings

[aarong]

1. AWS returns base64 strings for attribute values that contain XML-restricted characters (such as \u0000) -- detect and decode these values.
2. The XML parser used by aws-lib returns empty strings as {} -- check for these and return "" to the client.

[rjrodger]

Hi Aaron - just trying to understand this pull request - do you have a test case for the problem it is solving?
thanks!

[rjrodger]

Sorry for the lack of action on my part - I made you a collaborator, so feel free to merge directly :)

[tracend]

@aarong would like to know if this is addressed in later versions of aws-lib.

Should we close this request or update it?

[rjrodger]

I too out of the loop to comment, but note that I have made this project Open-Open: https://github.com/rvagg/node-levelup/blob/master/CONTRIBUTING.md