chore: update GitHub branch references

CONTRIBUTING.md

@@ -60,7 +60,7 @@ cd smtpapi-go
 
 ##### Execute: #####
 
-See the [examples folder](https://github.com/sendgrid/smtpapi-go/tree/master/examples) to get started quickly.
+See the [examples folder](examples) to get started quickly.
 
 To run the example:
 
@@ -85,9 +85,9 @@ smtpapi.go is the source code
 
 All PRs require passing tests before the PR will be reviewed.
 
-All test files are in the [`/`](https://github.com/sendgrid/smtpapi-go/tree/master/) directory.
+All test files are in the [`smtpapi_test.go`](smtpapi_test.go) file.
 
-For the purposes of contributing to this repo, please update the [`smtpapi_test.go`](https://github.com/sendgrid/smtpapi-go/blob/master/test/smtpapi_test.go) and [`smtpapi_test_strings.go`](https://github.com/sendgrid/smtpapi-go/blob/master/test/smtpapi_test_strings.go) files with unit tests as you modify the code.
+For the purposes of contributing to this repo, please update the [`smtpapi_test.go`](smtpapi_test.go) and [`smtpapi_test_strings.json`](smtpapi_test_strings.json) files with unit tests as you modify the code.
 
 To run the tests:
 
@@ -147,7 +147,7 @@ Please run your code through:
 5. Locally merge (or rebase) the upstream development branch into your topic branch:
 
    ```bash
-   git pull [--rebase] upstream master
+   git pull [--rebase] upstream main
    ```
 
 6. Push your topic branch up to your fork:
@@ -157,7 +157,7 @@ Please run your code through:
    ```
 
 7. [Open a Pull Request](https://help.github.com/articles/using-pull-requests/)
-    with a clear title and description against the `master` branch. All tests must be passing before we will review the PR.
+    with a clear title and description against the `main` branch. All tests must be passing before we will review the PR.
 
 <a name="code-reviews"></a>
 ## Code Reviews

README.md

@@ -1,6 +1,6 @@
-![SendGrid Logo](https://uiux.s3.amazonaws.com/2016-logos/email-logo%402x.png)
+![SendGrid Logo](twilio_sendgrid_logo.png)
 
-[![BuildStatus](https://travis-ci.org/sendgrid/smtpapi-go.svg?branch=master)](https://travis-ci.org/sendgrid/smtpapi-go)
+[![BuildStatus](https://travis-ci.org/sendgrid/smtpapi-go.svg?branch=main)](https://travis-ci.org/sendgrid/smtpapi-go)
 [![MIT licensed](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE.md)
 [![Email Notifications Badge](https://dx.sendgrid.com/badge/php)](https://dx.sendgrid.com/newsletter/php)
 [![Twitter Follow](https://img.shields.io/twitter/follow/sendgrid.svg?style=social&label=Follow)](https://twitter.com/sendgrid)
@@ -24,7 +24,7 @@
 # Announcements
 **The default branch name for this repository has been changed to `main` as of 07/27/2020.**
 
-All the updates to this library are documented in our [CHANGELOG](https://github.com/sendgrid/smtpapi-go/blob/master/CHANGELOG.md).
+All the updates to this library are documented in our [CHANGELOG](CHANGELOG.md).
 
 <a name="installation"></a>
 # Installation
@@ -73,22 +73,22 @@ func main() {
 # Usage
 
 * [SendGrid Docs](https://sendgrid.com/docs/API_Reference/SMTP_API/index.html)
-* [Example Code](https://github.com/sendgrid/smtpapi-go/tree/master/examples)
+* [Example Code](examples)
 
 # Roadmap
 
 If you are interested in the future direction of this project, please take a look at our [milestones](https://github.com/sendgrid/smtpapi-go/milestones). Your feedback will be highly appreciated.
 
 # How to Contribute
 
-We encourage contribution to our libraries, please see our [CONTRIBUTING](https://github.com/sendgrid/smtpapi-go/blob/master/CONTRIBUTING.md) guide for more details on contributions.
+We encourage contribution to our libraries, please see our [CONTRIBUTING](CONTRIBUTING.md) guide for more details on contributions.
 
 Quick links:
 
-* [Feature Request](https://github.com/sendgrid/smtpapi-go/blob/master/CONTRIBUTING.md#feature-request)
-* [Bug Reports](https://github.com/sendgrid/smtpapi-go/blob/master/CONTRIBUTING.md#submit-a-bug-report)
-* [Improvements to the Codebase](https://github.com/sendgrid/smtpapi-go/blob/master/CONTRIBUTING.md#improvements-to-the-codebase)
-* [Review Pull Requests](https://github.com/sendgrid/smtpapi-go/blob/master/CONTRIBUTING.md#code-reviews)
+* [Feature Request](CONTRIBUTING.md#feature-request)
+* [Bug Reports](CONTRIBUTING.md#submit-a-bug-report)
+* [Improvements to the Codebase](CONTRIBUTING.md#improvements-to-the-codebase)
+* [Review Pull Requests](CONTRIBUTING.md#code-reviews)
 
 <a name="about"></a>
 # About