Convert specs to RSpec 3.0.1 syntax with Transpec

This conversion is done by Transpec 2.2.4 with the following command:
    transpec --convert example_group

* 2 conversions
    from: describe 'something' { }
      to: RSpec.describe 'something' { }

For more details: https://github.com/yujinakayama/transpec#supported-conversions