Slightly improved S3 compatibility

- ListBucket does not require any of the parameters (delimiter,
    prefix, max-keys, etc)
- URLs are properly percent_decoded
- PutObject and DeleteObject calls now answer correctly
    (empty body, version id in the x-amz-version-id: header)

src/api/Cargo.toml

@@ -30,5 +30,5 @@ http = "0.2"
 hyper = "0.13"
 url = "2.1"
 httpdate = "0.3"
-
+percent-encoding = "2.1.0"