Signature calculation has now moved out from being a package to
top-level as a layered mechanism.
In case of payload calculation with body, go-routines are initiated
to simultaneously write and calculate shasum. Errors are sent
over the writer so that the lower layer removes the temporary files
properly.
Optimizing List Objects by using binary sort to discard entries in cases
where prefix or marker is set.
Adding test coverage to ListObjects.
Adding benchmark to ListObjects.
Harshavardhana