feat(cli): pass cloudformation parameters to "cdk deploy"

Adding an example of using parameters to the README.md

packages/aws-cdk/README.md

@@ -136,9 +136,15 @@ and always deploy the stack.
 In order to pass parameters to your template during deployment, you can use `--parameters
 (STACK:KEY=VALUE)`. This will apply the value `VALUE` to the key `KEY` for stack `STACK`. The stack
 name can either be `*` or omitted in order to apply to all stacks.
-Note: The parameters will not propagate to NestedStacks. These has to be sent with the constructor
+Note: The parameters will not propagate to NestedStacks. These must be sent with the constructor
 of these.
 
+An example of this could be:
+
+```console
+$ cdk deploy --app='node bin/main.js' --parameters 'MyStackName:MyKey=HelloWorld'
+```
+
 #### `cdk destroy`
 Deletes a stack from it's environment. This will cause the resources in the stack to be destroyed (unless they were
 configured with a `DeletionPolicy` of `Retain`). During the stack destruction, the command will output progress