Unwind resources that were defined more than once

This fixes a bug where a resource defined more than once would get removed
from the `run_context.resources` array once per definition, but the indexes in
`run_context.resources_by_name` would only get offset by 1.
Convert specs to RSpec 3.1.7 syntax with Transpec

This conversion is done by Transpec 3.0.1 with the following command:
    transpec -f

* 1 conversion
    from: == expected
      to: eq(expected)

* 1 conversion
    from: obj.should
      to: expect(obj).to

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