Tutum

- add environment proxy
- add support of TUTUM_REST_HOST and TUTUM_STREAM_HOST
- add the support of image tags

API improvements and several fixes

use latest version of docker-py and requests

1. print logs to stderr if it is from standard error
2. print source of the log if available
3. add Action class
4. add AZ(availability zone) class
5. add user-agent to both REST api and web socket
6. switch the lookup of stack.container to container.stack,
7. switch the lookup of stack.service to service.stack
8, add ping/pong to web socket, solving the issue of reconnect

- allow fetching a remote container by using stack_name.container_name
- allow fetching a remote service by using stack_name.service_name

- rename webhookhandler to trigger
- add nodecluster upgrade
- add scale endpoint to service
- show logs through streaming API