sort all signParams
shorter initial sentence in godoc
Adding support for signing using IAM User temporary credentials.
don't crash when an http request fails
omit needless xml indentation
s3util: automatically increase part size

This enables uploading any size object (up to the
Amazon-imposed maximum of 5TiB) while doing as
little buffering as possible for smaller objects.
be sure part size doesn't overflow
test vhost bucket derivation
test with literal Service definition

User may have copied out the definition of DefaultService.
To keep compatibility, the definition as written here must
continue to work.
Support signing for third-party services.
Update package description
move example code to separage package
Fix signature sorting of common prefix keys.

The AwzHeaders need to be sorted by key, not
key+value.
configurable http client
always close the response body
don't hold on to unneeded buffers
comment style
one more AmazonBucket example