Fix class~instance matchers in Array specs

Many specs are using the `be_kind_of` matcher.
But in most cases, they aim to check instance~class relationships.
An example is #197.
And as below spec.

### Example

```ruby
describe "SuperClass#foo" do
  it "does not return SubClass instance" do
    Subclass.new.foo.should be_kind_of(SuperClass)
  end
end
```

The `be_kind_of` matcher depends #is_a?  in mspec.
And this spec passes when the example is a SubClass instance.

I think these specs should depend #instance_of? and the `be_an_instance_of` matcher.