Adding repro for #110

Currently fails due to lack of protected serialisation ctor.
Replace PreserveStackTrace method implementation (#110)

Based on: http://stackoverflow.com/a/9989557/906
Update changelog
Updating changelog for 1.6.1 release
Website update for 1.6.1
updating nuget
Updating to Castle.Core.3.2.0 (from 3.1.0)
add a unit test for PossibleIssue_ArgumentCheckOfOptionalParameter
Marking Issue_ArgumentCheckOfOptionalParameter as [Pending] test
Partial subs. #41 #93

[dave@davesquared.net: squashed into single commit for easier rebase]
Reverting ThatCallsBase option until we clarify requirement and syntax
Moving CallBaseFor tests from SubstituteExtensions to top level acceptance test
Throw on attempt to call base on non-virtual

Throwing CouldNotCallBaseException as soon as abstract/final member is
called.

Removing tests that attempt to configure non-virtual members.
Spiking configuring CallBase using returns
I changed the api to sub.DoSomething().Returns(x => x.CallBase())
Ensuring base method is only evaluated once per call
Adding partial substitute examples
Adding breaking test for #118 (an issue after adding a public static method to a concrete class that is being mocked)
Excluded static methods when determining if a type is pure virtual (Fixes #118)
Also added a (already passing) test that checks that a substitute for a concrete with a static method can setup a return value to improve coverage of this type of class
Added documentation for the changes that were made in the last commit