Add better `inspect` output for ExampleGroup

Pull Request for #1590 

The only problem I ran into was that the syntax error in the after hook test produces error output while running the spec (the test still passes).

> An error occurred in an `after(:context)` hook.
>   NoMethodError: undefined method `expcts' for #<RSpec::ExampleGroups::SomeClass_3 after(:context) hook>

This is definitely not ideal because it could distract from problems with "real" after hooks. The only two options I could up with were: 1) remove the test, or 2) add a way to suppress that error. I'm interested in your thoughts on the best way to handle this.
I think I'm going to get rid of this spec. It's very similar to:

```ruby
        it 'includes description and location' do
          an_example = nil

          line = __LINE__ + 2
          group = ExampleGroup.describe 'SomeClass1' do
            example 'an example' do
              an_example = self
            end
          end

          group.run

          path = RSpec::Core::Metadata.relative_path(__FILE__)
          expect(an_example.inspect).to eq("#<RSpec::ExampleGroups::SomeClass1 \"an example\" (#{path}:#{line})>")
        end
```