bugfix and small feature release

Fixes pkg#234: fix client deadlock on server death during writes

Feature: Added ability to set MaxPacket size for the clients to values
outside those accepted by Openssh's SFTP server. To support servers with
differing capacities.

New context.Context in Request server

Added context.Context support for the Request server.
Remove unnecessary gcc special cases.

New errors, documentation and dropping go<=1.7

New request-server errors for explicitly controlling returned status code.
Drop go <= 1.7 support.
Documentation improvements.

Small feature and bugfix release.

Feature: Add helper functions to the request object for working with
bitmask flags and file attributes.

Fix: Corrctly handled errors coming from the backend on file Open w/
create flag.

New bugfix release. Mainly bug w/ windows volumes.

Fixes issue pkg#217; Fix volume name mangling on windows

Open-packet's pflags (file opening flags) now saved in Request.Flags
since in cases of SSH_FXF_CREAT being set a 0 len Write call is made.

Also continuing some refactoring to simplify and clean up the request
based code. In this case I removed an unnecessary data structure storing
packet data.

New bugfix release. Fixes request-server issues.

Fix issue pkg#214; request-server doesn't handle uploads of empty files
Fix issue pkg#215; request-server: problem with Request.setFileState()

Also a small refactor of the Request struct and how it is stored and
updated. Simplifies things and reduces garbage.

New bugfix and minor feature release

Fixes pkg#207, a problem with the server returning bad paths
Adds PR pkg#213, adds PosixRename (OpenSsh extention) to client

Bugfix and documentation release.

Initial release using Semantic Versioning.