v4.0.0

Breaking Change

• Pull request #261
• BIG THANKS to Adam Buczynski!!!

Fixed

• Issue #240
• Issue #246
• Issue #206

Added

• Extracted some logic into helpers
• Using a getEmptyRequest helper to avoid code duplication
• emtpyRequest now accepts an object with data to extend the empty request with, this will allow simpler syntax for initializing requests.
• Callback function now receives two parameters as per Node conventions (error, response)
• If no callback provided, the method will return a promise instead.
• Implemented promise API when not passing a callback function
• Using native Promise by default if present, but allow users to override this with any other implementation by setting Sendgrid.Promise to any value, e.g. Sendgrid.Promise = require('bluebird')