Update README.md

Merge pull request vapor-community#39 from MihaelIsaev/master

Fix `IncomingMessage` model and update to Vapor4 RC with Swift 5.2

Merge pull request vapor-community#37 from MihaelIsaev/master

Upgrade to Vapor4

Merge pull request vapor-community#35 from saicu/master

Multiple Domain Configuration

Merge pull request vapor-community#34 from saicu/master

fix for sending without template data

Merge pull request vapor-community#32 from saicu/master

Mailgun templates

Merge pull request vapor-community#31 from madsodgaard/feature/eu-sup…

…port

Add support for region selection

Merge pull request vapor-community#29 from AAAstorga/master

Add inline support

Merge pull request vapor-community#20 from rafiki270/master

readme update for the new code

Merge pull request vapor-community#17 from MihaelIsaev/patch-1

Implement replyTo