Rename CookieSessionStore to CookieSessionHandler
Pull out session data object into it's own file
Use a default max-age rather than expiry
Sessiondata supports GobEncoder/GobDecoder interface
Simplify session handler logic
Update interface to use a session finder function rather than a full struct
Make signedcookiehandler private
Can't use gob interface recursively
Test non-existent keys
Update handler test with new session interface
Fix test for clearing session
Detect IE user agent and use Expires instead of Max-Age
Rewrite cookie_signer and tests
Use new cookie_signer in signed_cookie
Merge pull request #35 from 99designs/features/session-maxage-2

Sessions should use max-age