Fixed issue with method with sealed class return type
Spiking Substitute.ForPartsOf<T>

Renabling @alexandrnikitin's initial call base by default idea to
  see if it better fits the examples I'm seeing.

Adding basic Maybe type, as no one should have to code without one.

TODO:
- decide whether to remove explicit CallBase option
- enable DoNotCallBase() for void calls? When().DoNotCallBase()?
- add overloads for Substitute.ForPartsOf.
- throw on Substitute.ForPartsOf if an interface is given
In progress, removing CallBase()
Adding call base exclusions (When..DoNotCallBase)
Cleaning up some unused code.
Replace boolean callBaseByDefault with SubstituteConfig enum
Updating Substitute.ForPartsOf xmldoc.
Updating CHANGELOG for partial subs.
Adding documentation for partial subs.
Move Received.InOrder from Experimental to main namespace
Updating CHANGELOG and BreakingChanges for 1.7.0 release.
Updating NuGet.exe to 2.7.3 (from 2.6.0)
Updating website for 1.7.0 release
Repro for ambiguous args with out/ref bug (#129)
#129 Ambiguous args with out/ref arg

Fixed by adding IsOut ParameterType exception to NonParamsArgumentSpecificationFactory
Adding test for working out arg spec for out parameter
Updating CHANGELOG for 1.7.1 release
Updating docs for 1.7.1 release
Add Net45 to Rakefile
Create a .NET 4.5 configuration