Adding check for Class types

Stubbing a selector in the following way would fail:

```
[myObject stub:@selector(doSomethingWithClass:) withArguments:[NSString class]];
```

The Class argument was being treated like a non-object primitive.
Merge pull request #1 from mindsnacks/check-for-class-type-when-matching

Adding check for Class types
Add test for class type check.
Merge pull request #2 from modocache/mindsnacks-pr460-add-test

Add test for class type check.
Merge pull request #460 from mindsnacks/master

Adding check for Class types