Solve deprecated warnings by changes RSpec 2 to 3.

- `example.execution_result` became `Hash` to `RSpec::Core::Example::ExecutionResult`
- Key that get parent example group metadata changes `:parent_example_group`
Create TurnipFormatter::Helper that has role to absorb the difference RSpec2 and 3.
Merge pull request #47 from gongo/deprecated_warnings_of_metadata

Solve deprecated warnings by changes RSpec 2 to 3.