Issue Summary

In the Travis CI and local environment:

1. Download the appropriate Prism binary (if it does not exist on the system)
2. Start Prism, using SendGrid's swagger (oai) definition
3. Run the Unit Tests
4. Shut Down Prism

References

https://stoplight.io/prism
https://raw.githubusercontent.com/sendgrid/sendgrid-oai/master/oai_stoplight.json

We have already done this in these libraries:

Python:
https://github.com/sendgrid/sendgrid-python/blob/master/.travis.yml#L14
https://github.com/sendgrid/sendgrid-python/blob/master/test/prism.sh
https://github.com/sendgrid/sendgrid-python/blob/master/test/test_sendgrid.py#L22

PHP:
https://github.com/sendgrid/sendgrid-php/blob/master/.travis.yml#L3
https://github.com/sendgrid/sendgrid-php/blob/master/test/prism.sh
https://github.com/sendgrid/sendgrid-php/blob/master/test/unit/SendGridTest.php#L13

C#:
https://github.com/sendgrid/sendgrid-csharp/blob/master/.travis.yml#L9
https://github.com/sendgrid/sendgrid-csharp/tree/master/prism
https://github.com/sendgrid/sendgrid-csharp/blob/master/SendGrid/UnitTest/UnitTest.cs#L23

Go:
https://github.com/sendgrid/sendgrid-go/blob/master/.travis.yml#L4
https://github.com/sendgrid/sendgrid-go/blob/master/prism.sh
https://github.com/sendgrid/sendgrid-go/blob/master/sendgrid_test.go#L35