Snapshot prototype for POX

Includes integration test.
Rename demo config file
Merge branch 'master' of github.com:ucb-sts/sts into snapshot_prototype
Merge branch 'master' of github.com:ucb-sts/sts into snapshot_prototype
Fix bug: pass_through events should be sorted by time
Implement 'record-only' mode, where messages are received but not sent to the network.

Also remove apparently repeated methods "set_pass_through" and
"unset_pass_through"
Merge pull request #12 from ucb-sts/snapshot_prototype

Snapshot prototype