Add bit about semantics of push notification delivery guarantees
Merge pull request #16 from nikhilm/develop

Add bit about semantics of push notification delivery guarantees
changing from DOMRequest to Promise
changing version to unsigned long long and clarifying when it is nullable
removing serverProtocols
addressing Jonas' concern about transfering actual content in notifications
fix example 1 to use Promise
fixing Promise-related descriptions
adding links to promises algorithms
Merge pull request #17 from efullea/develop

Addressing Mozilla's comments