Essh

* fixed bug with python3 and exceptions

* added support for AWS_SESSION_TOKEN
* added --zone option to filter instances to a specific zone. Useful when SSHing into an autoscaling group where all the instances have the same name. Zone is also used to specify the region so you don't need a profile for every region.
* added --profile option to read the AWS credentials from the named profile.

* fixed a bug with ssh commands that contain options like "tail -f"

- If no username command fails, it will try various common usernames until one works.

- add indexing syntax and the ability to run commands