Retry POST request with cookie authentication

I am using CAS with cas-rest-client and mod_auth_cas.

When I send mod_auth_cas a POST request with ticket authentication, it sends a 302 redirect with a MOD_AUTH_CAS cookie. Since 302 redirects must not be automatically followed for POST, RestClient raises the Found exception which propagates out through CasRestClient.

If I handle this case in CasRestClient and re-submit the POST request using cookie-based authentication, the requests succeeds.

This pull request includes a first commit which adds rspec to the gemspec and organizes the rspec tests.

The second commit adds the redirect retry support.