Add AutoFixture.AutoFoq project to Testing Tools

This pull request originates from [this](https://github.com/fsprojects/fsprojects.github.io/issues/5#issuecomment-62634180) comment – it adds [AutoFixture.AutoFoq](http://www.nuget.org/packages/AutoFixture.AutoFoq) to the Testing Tools section.

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AutoFixture.AutoFoq turns [AutoFixture](http://www.nuget.org/packages/AutoFixture) into an [Auto-mocking Container](http://blog.ploeh.dk/2013/03/11/auto-mocking-container/) where the mock instances are created by [Foq](https://github.com/fsprojects/Foq).

**Typical usage**

In the test below the mocked instance is created automatically by Foq:

```f#
[<Fact>]
let AutoMockInterfaceAndSetupExpectations() =
    // Fixture setup
    let fixture = Fixture().Customize(AutoFoqCustomization())
    let dummy = obj()
    // Exercise system
    let sut = fixture.Create<IInterface>()
    sut.MakeIt(dummy) |> ignore
    // Verify outcome
    Mock.Verify(<@ sut.MakeIt(dummy) @>, Times.Once)
    // Teardown
```

**Integration with xUnit.net**

The above test can be written declaratively using xUnit.net's data theories:

```f#
[<Theory>][<AutoFoqData>]
let AutoMockInterfaceAndSetupExpectationsDeclaratively 
  (sut : IInterface, dummy : obj) =
    sut.MakeIt(dummy) |> ignore
    Mock.Verify(<@ sut.MakeIt(dummy) @>, Times.Once)
```

The `[AutoFoqData]` attribute is defined as:

```f#
type AutoFoqDataAttribute() = 
    inherit AutoDataAttribute(
        Fixture().Customize(AutoFoqCustomization()))
```