add handling of content_type code reference in App/File (readable change)
add attribute content_type to Middleware/Static which can be an callback
provide tests for content_type callback for Plack::App::File and Plack::Middleware::Static.
Using Plack::MIME with added mimetype and modify the returned mimetype to make sure it is not the Plack::MIME fallback which was called. This was done not to have a dependency to a different mimetype checker.
Documentation update
Merge pull request #361 from pstadt/middleware-static-contenttype

Use alternatives instead of Plack::MIME