Added stream functions

[harrysinghtiwana]

I have added some more useful methods to enhance the API functionalities for the followings;

Added method getDeltaCursor() to fetch the latest delta cursors Added method getDeltas() to fetch the deltas as per cursor in raw format. Added method getCalenders() to fetch the calendars. Added method getDeltaStream() to fetch the detlas in an array as per include types. Added method getContacts() to fetch the contacts. Added reusable methods such as setApiClientOptions() and createAuthHeader() as well.

[duxet]

Hey, you might want to take a look at my fork: https://github.com/O323/nylas-php