record session_started
rename session_started -> session_refreshed_at

the timestamp being used is refreshed every so often and doesn't
actually indicate the *start* of the session
Merge pull request #2 from lukfugl/session_started

record session_refreshed_at
bump to 1.0.3
fix calculation of session_refreshed_at timestamp

the timestamp stored in the encrypted cookie already represents the
"session_refreshed_at" value. in 1.0.3 we incorrectly interpreted it as
a "expires_at" value, as if it already included the expire_after value
Merge pull request #3 from lukfugl/session_started

fix calculation of session_refreshed_at timestamp
bump to 1.0.4
update gem date