Unable to Instantiate a new MailService class

[krazibit]

Issue Summary

Unable to instantiate the MailService class as it thought to be a property by TS

Steps to Reproduce

import {MailService} from '@sendgrid/mail'
const ms = new MailService()

Error : Cannot use 'new' with an expression whose type lacks a call or construct signature.

Technical details:

• sendgrid-nodejs Version: 6.4.0
• Node.js Version: 10.15.3

[childish-sambino]

Fixed by #921