Merge pull request #1 from avalade/master

Updated to use version 0.8.5 of dispatch-core
Fixing a bug concerning usage of x-amz headers.

Usage of x-amz headers generally led to an exception while
building the map of headers.
Merge pull request #2 from dwestheide/fix_amazon_headers

Fixing a bug concerning usage of x-amz headers.
Adding a way to generate signed request URIs.

Signed request URIs can be used with the query string
authentication of S3, so that third parties without a
secret key can get access to specific resources.
Updating README
Merge pull request #3 from dwestheide/signed_uri_generation

Signed uri generation
released 0.8.8 which only cares about 2.9.1
added 2.10 as a build target