Updated Codecov badge to Official repo link

Author: gr8shivam

README.md

@@ -1,7 +1,7 @@
 ![SendGrid Logo](https://uiux.s3.amazonaws.com/2016-logos/email-logo%402x.png)
 
 [![Travis Badge](https://travis-ci.org/sendgrid/sendgrid-python.svg?branch=master)](https://travis-ci.org/sendgrid/sendgrid-python)
-[![codecov](https://codecov.io/gh/meahow/sendgrid-python/branch/issue_251_coverage/graph/badge.svg)](https://codecov.io/gh/meahow/sendgrid-python)
+[![codecov](https://img.shields.io/codecov/c/github/sendgrid/sendgrid-python/master.svg?style=flat-square&label=Codecov+Coverage)](https://codecov.io/gh/sendgrid/sendgrid-python)
 [![Docker Badge](https://img.shields.io/docker/automated/sendgrid/sendgrid-python.svg)](https://hub.docker.com/r/sendgrid/sendgrid-python/)
 [![Email Notifications Badge](https://dx.sendgrid.com/badge/python)](https://dx.sendgrid.com/newsletter/python)
 [![MIT licensed](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE.txt)