v0.37.0.
Now multiple subscriptions supports multiple callback execution on
every message received. Fixed pubsub logic.
Updated Libra to v0.15.0, removed useless logic.
Fixed bugs with multiple (p)(un)subscriptions.
Added new pubsub-mode tests and fixed old ones.
On branch pubsub
modified:   Readme.md
modified:   lib/spade.js
modified:   package.json
modified:   test/pubsub-mode-offline-test.js
modified:   test/pubsub-mode-test.js