Problem Details for HTTP APIs release v05

- Media type change from "application/api-problem+json" to "application/problem+json".
- Problem details object member "problemType" was renamed from "problemType" to "type".
- Problem details object member "httpStatus" was renamed from "httpStatus" to "status".
- Change RFC URI
Merge pull request #11 from gsc-frank/rfc-update-to-v05

Problem Details for HTTP APIs released v05
[#11] Fix unit test

- Was still referring to `http_status`, instead of `status`.
Merge branch 'feature/11'

Close #11