Role can now be attached/replaced at runtime

See http://stackoverflow.com/questions/35913966/how-to-add-iam-role-to-an-existing-instance-in-aws
This is also available via the Console under "Actions >Instance Setting > Attach/Replace IAM role".

README.md

@@ -790,7 +790,6 @@ EC2
 -	❗If the EC2 API itself is a critical dependency of your infrastructure (e.g. for automated server replacement, custom scaling algorithms, etc.) and you are running at a large scale or making many EC2 API calls, make sure that you understand when they might fail (calls to it are [rate limited](http://docs.aws.amazon.com/AWSEC2/latest/APIReference/query-api-troubleshooting.html#api-request-rate) and the limits are not published and subject to change) and code and test against that possibility.
 -	❗Many newer EC2 instance types are EBS-only. Make sure to factor in EBS performance and costs when planning to use them.
 -	❗⏱ Instances come in two types: **Fixed Performance Instances** (e.g. M3, C3, and R3) and [**Burstable Performance Instances**](https://aws.amazon.com/ec2/instance-types/#burst) (e.g. T2). A T2 instance receives CPU credits continuously, the rate of which depends on the instance size. T2 instances accrue CPU credits when they are idle, and use CPU credits when they are active. However, once an instance runs out of credits, you'll notice a severe degradation in performance. If you need consistently high CPU performance for applications such as video encoding, high volume websites or HPC applications, it is recommended to use Fixed Performance Instances.
--	🔸An IAM role can be assigned to an EC2 instance [only at launch time](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_switch-role-ec2.html). You cannot assign to a running instance.
 -        Instance user-data is [limited to 16 KB](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html#instancedata-add-user-data). (This limit applies to the data in raw form, not base64-encoded form.) If more data is needed, it can be downloaded from S3 by a user-data script.
 -        Very new accounts may not be able to launch some instance types, such as GPU instances, because of an initially imposed “soft limit” of zero. This limit can be raised by making a support request. See [AWS Service Limits](http://docs.aws.amazon.com/general/latest/gr/aws_service_limits.html) for the method to make the support request. Note that this limit of zero is [not currently documented](http://docs.aws.amazon.com/general/latest/gr/aws_service_limits.html#limits_ec2).