Display nested describes & contexts as subtrees

[Arthaey]

Your environment

• vscode-ruby-test-adapter version: 0.6.1
• Ruby version: ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-darwin15]
• VS Code version: 1.41.1
• Operating System: Mac OS X El Capitan (10.11.5)
• RSpec version: 3.8.0

Expected behavior

When I use nested describes or contexts, I want them to be displayed in the Test Explorer as subtrees that reflect how I've organized the code.

describe "Foo" do
    it "CORRECT: nested 1 level deep, directly under filename"

    context "Bar" do
        it "REQUEST: should be nested 2 levels deep"
    end
end

> example_spec.rb
  - Foo CORRECT: nested 1 level deep, directly under filename
  > Foo Bar
    - REQUEST: should be nested 2 levels deep

Actual behavior