Update specs to RSpec 2.14.8 syntax

This conversion is done by Transpec 1.13.1 with the following command:
    transpec

* 78 conversions
    from: obj.should
      to: expect(obj).to

* 52 conversions
    from: its(:attr) { }
      to: describe '#attr' do subject { super().attr }; it { } end

* 35 conversions
    from: == expected
      to: eq(expected)

* 8 conversions
    from: obj.should_not
      to: expect(obj).not_to

* 2 conversions
    from: it { should have(n).keys }
      to: it 'has n keys' do expect(subject.keys.size).to eq(n) end