HaveClass and NotHaveClass take params

[srpeirce]

At the moment we need to call HaveClass multiple times to assert multiple classes.

Render(@<button Class="btn big cta"><h1>Test</h1></button>)
            .Should().HaveClass("btn")
            .And.HaveClass("big")
            .And.HaveClass("cta");

It would be nice to take params for cleaner syntax:

Render(@<button Class="btn big cta"><h1>Test</h1></button>)
            .Should.HaveClasses("btn", "big", "cta");