Fix scan: the cursor is returned as a long in redis-py.

This caused --use-redis tests to hang.
Merge pull request #71 from mikekap/feature/fix_scan

Fix scan: the cursor is returned as a long in redis-py.
Fix the TTL -1/-2/None confusion - it varies by strictness.

-1/-2 are returned by StrictRedis; None is returned when using non-strict.
Merge pull request #72 from mikekap/feature/fix_ttl

Fix the TTL -1/-2/None confusion - it varies by strictness.