refactor opening files/dirs in request-server

Minor version bump due to a pretty heavy refactoring of the
request-server's handing of open packets. It now calls through to the
handler to initialize the reader/writer/lister objects when it receives
the open packet. This should be transparent and was done in relation to
a bug fix, but it is a pretty major refactor so the minor version bump.

Fixed #280; Request.WithContext() deadlock when called from handler

fixes tests to run on windows