Add net40 support (statianzo#261)

* Add support for the .NET 40 framework

* Don't use the SetSocketOption for the NET40. Some bugs are appearing on Windows XP

* Add readonly property SupportDualStack with default value to true

* Replacing NET45, NET40 switches with a method IsRunningOnWindows

Possible performance improvement in Hybi13Handler (statianzo#260)

Allow change default keep alive settings to run on Windows only (stat…

…ianzo#233)

The method "Socket.IOControl" is only available on Windows platform, we need to check before using its.

This pull request contains the changes described in statianzo#232, with no tab/space changes.

Tentative fix for missing Update-AppveyorBuild function - use PS over…

… PSCore.

Tentative fix for missing Update-AppveyorBuild function - use PS over…

… PSCore.

link nuget

fix for incompatible address on restart (statianzo#186)

Previously when a listener would restart because of an error while on
an IPv6 address it would give an error ‘An address incompatible with
the requested protocol was used’. This fixes the issue.

Merge pull request statianzo#181 from jespertheend/restart-listner-wi…

…th-flag

added RestartAfterListenError

Bump to 0.11.1

Bump to 0.11.0