Adding documentation for MetaKey support

Author: gnongsie

README.md

@@ -48,14 +48,24 @@ Additionally, you can find details and examples of how our API is structured in
 
 The API Reference Guide provides examples of what information is needed for a particular request and how that information would be formatted. Using those examples, you can easily determine what methods would be necessary to include that information in a request using this SDK.
 
+## MetaKey Support
+
+A Meta Key is a single key that can be used by one, some, or all merchants (or accounts, if created by a Portfolio user) in the portfolio.
+
+The Portfolio or Parent Account owns the key and is considered the transaction submitter when a Meta Key is used, while the merchant owns the transaction.
+
+MIDs continue to be able to create keys for themselves, even if a Meta Key is generated.
+
+Further information on MetaKey can be found in [New Business Center User Guide](https://developer.cybersource.com/library/documentation/dev_guides/Business_Center/New_Business_Center_User_Guide.pdf).
+
 ### Switching between the sandbox environment and the production environment
 Cybersource maintains a complete sandbox environment for testing and development purposes. This sandbox environment is an exact duplicate of our production environment with the transaction authorization and settlement process simulated. By default, this SDK is configured to communicate with the sandbox environment. To switch to the production environment, set the `runEnvironment` property in the SDK Configuration.  See our sample at https://github.com/CyberSource/cybersource-rest-samples-ruby/blob/master/data/Configuration.rb
 
 ```Ruby
-# For TESTING use
-runEnvironment='cybersource.environment.sandbox'
-# For PRODUCTION use
-# runEnvironment='cybersource.environment.production'
+   # For TESTING use
+   runEnvironment='cybersource.environment.sandbox'
+   # For PRODUCTION use
+   # runEnvironment='cybersource.environment.production'
 ```
 
 API credentials are different for each environment, so be sure to switch to the appropriate credentials when switching environments.