Refactor extensions on object

[KristianWedberg]

The library has several extension methods on object (WithDeepEqual etc.) This makes them pollute Intellisense for all class objects, which is quite annoying.

I suggest refactoring to instead use non-extension methods, e.q. DeepEqual.IsEqual(ob1, ob2) etc.

[jamesfoster]

Its done that way to make your tests more readable. The same way Shouldly adds ShouldEqual etc to Object. This won't change.