Added link to GitHub discussion about using MFA in the ECS CLI.

README.md

@@ -102,12 +102,14 @@ Create a cluster configuration with the following command, substituting `region_
 
 The first Cluster Configuration or ECS Profile that you configure will be set as the default. The default ECS Profile can be changed using the `ecs-cli configure profile default` command; the default cluster configuration can be changed using the `ecs-cli configure default` command. Note that unlike in the AWS CLI, the default ECS Profile does not need to be named "default".
 
-### Using Credentials from `~/.aws/credentials` and Assuming a Role
+### Using Credentials from `~/.aws/credentials`, Assuming a Role, and Multi-Factor Authentication
 
 The `--aws-profile` flag and `$AWS_PROFILE` environment variable allows you to reference any named profile in `~/.aws/credentials`.
 
 Here is an example on how to assume a role: [amazon-ecs-cli/blob/master/ecs-cli/modules/config/aws_credentials_example.ini](https://github.com/aws/amazon-ecs-cli/blob/master/ecs-cli/modules/config/aws_credentials_example.ini)
 
+If you are trying to use Multi-Factor Authentication, please see this comment and the associated issue: [#284 (comment)]https://github.com/aws/amazon-ecs-cli/issues/284#issuecomment-336310034.
+
 ### Order of Resolution for credentials
 
 1) ECS CLI Profile Flags