Do not check expected status as part of filling response body

The class method Excon::Response#parse checks the expected status as part of deciding which method to use to fill the response body. I think that the response body should be generated regardless of whether or not the status was as expected -- it is the response body, and it should be provided to the client.

The current implementation may not provide the response body to the client if the status was not expected and a response block was specified. This causes problems, e.g., in using VCR to record a response from AWS with status 400.

Please see https://github.com/geemus/excon/issues/264

Do we lose a particular use case by dropping the expected status check? In my local testing, I am now able to use VCR to record 400 responses from AWS.