Ensure text/plain & text/html content typs are handled and add missing specs for handled HTTP status codes

Add rspec-parameterized gem

Handle multiple content types

It's possible that responses from /api/v4/allowed could be of varying content type, so we now handle:

• application/json
• text/html
• text/plain

Renamed tests/VCR files to correct names:

• git push = git-receive-pack
• git pull = git-upload-pack

Added missing specs for GitlabNet#check_access()

• Added specs for:

  • git pull but access is denied (and returns 401)

  • git pull but access is denied (and returns 401 with text/html)

  • git pull but access is denied (and returns 401 with text/plain)

  • git push for project that doesn't exist (and returns 200)

  • git push but access is denied (and returns 401)

  • git push but access is denied (and returns 401 with text/html)

  • git push but access is denied (and returns 401 with text/plain)

  • git push for project that doesn't exist (and returns 404)

  • git push for project that doesn't exist (and returns 404 with text/html)

  • git push for project that doesn't exist (and returns 404 with text/plain)

• Added expectation around message attr

Closes #154 (closed) Related https://gitlab.com/gitlab-org/gitlab-ee/issues/6533