Fix changed underlying API
Validate certificates on API endpoints

This verifies a backend before an attempt is made to connect to it,
unfortunately without enforcing any strict guarantees about transport
security on the live connection itself, owing to shortcomings in the
stdlibs ssl support.
Require ssl backport on Python 2.5
Encode certificate data before hashing
refactor ssl cert checking a bit
fix python 2.5 syntax error
Merge pull request #68 from stripe/richo-certificate-blacklists

Implement certificate blacklists