fix(contrib/ec2): fix README from #865

There was a mistake in #865 - we want to add the pubkey for
~/.ssh/deis

Author: carmstrong

contrib/ec2/README.md

@@ -22,7 +22,7 @@ Default output format [None]:
 Generate and upload a new keypair to AWS, ensuring that the name of the keypair is set to "deis".
 ```console
 $ ssh-keygen -q -t rsa -f ~/.ssh/deis -N '' -C deis
-$ aws ec2 import-key-pair --key-name deis --public-key-material file://~/.ssh/deis
+$ aws ec2 import-key-pair --key-name deis --public-key-material file://~/.ssh/deis.pub
 ```
 
 ## Customize cloudformation.json