[API::PodsController] Add endpoints to serve spec data

GET /api/v1/pod/:name/spec
GET /api/v1/pod/:name/spec/:version
[API::PodsController] Use specs as endpoint, and require explicit 'latest' version
[PodsControllerSpec] Add specs for /api/v1/pods/:name/specs routes
Merge pull request #109 from CocoaPods/seg-spec-redirect

[API::PodsController] Add endpoints to serve spec data