Merge pull request #39 from thepriefy/priefy-issue-34-1

Add a .env_sample file

Author: Matt Bernier

.env_sample

@@ -0,0 +1 @@
+export SENDGRID_API_KEY=''

README.md

@@ -31,6 +31,18 @@ All updates to this library is documented in our [CHANGELOG](https://github.com/
 
 - Ruby version 2.2+
 
+## Setup Environment Variables
+
+### Environment Variable
+
+Update the development environment with your [SENDGRID_API_KEY](https://app.sendgrid.com/settings/api_keys), for example:
+
+```bash
+echo "export SENDGRID_API_KEY='YOUR_API_KEY'" > sendgrid.env
+echo "sendgrid.env" >> .gitignore
+source ./sendgrid.env
+```
+
 ## Install Package
 
 ```bash