feat(pkg/console): support interactive console

[giannoul]

This PR introduces the support for interactive console

requires teamhephy/controller#148

Using a github.com/gorilla/websocket we access the k8s API in order to create an interactive console with a container like so:

deis apps:create testadminapp5 --no-remote
Creating Application... done, created testadminapp5
If you want to add a git remote for this app later, use `deis git:remote -a testadminapp5`

deis config:set PORT=5000 --app=testadminapp5
Creating config... done

=== testadminapp5 Config
PORT      5000

deis builds:create igiannoulas/sample-flask-app:v0.1.2 --procfile="{web: python3 app/app.py}" --app=testadminapp5
Creating build... done

deis ps:list -a testadminapp5
=== testadminapp5 Processes
--- web:
testadminapp5-web-6f5b688cb9-jw2wb up (v3)

deis ps:console testadminapp5-web-6f5b688cb9-jw2wb web testadminapp5 /bin/sh --debug=true
Starting console session with command /bin/sh for pod testadminapp5-web-6f5b688cb9-jw2wb for application testadminapp5
INFO[0000] [Start] Container name: testadminapp5-web
INFO[0000] [RoundTrip] Url: wss://10.0.0.119:8443/api/v1/namespaces/testadminapp5/pods/testadminapp5-web-6f5b688cb9-jw2wb/exec?stdout=true&tty=true&command=/bin/sh&container=testadminapp5-web&stdin=true
INFO[0000] [RoundTrip] Decoded token: eyJhbGciOi ... 4vekvJFY_w
# ls
Dockerfile  bin   etc   lib64  opt               root  srv  usr
Procfile    boot  home  media  proc              run   sys  var
app         dev   lib   mnt    requirements.txt  sbin  tmp
# ps faux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root        28  0.0  0.0   4504   704 pts/0    Ss   14:20   0:00 /bin/sh
root       106  0.0  0.0  34424  2840 pts/0    R+   14:25   0:00  \_ ps faux
root         1  0.0  0.3  76128 25892 ?        Ss   14:18   0:00 python3 app/app
root         8  0.3  0.3 233960 26544 ?        Sl   14:18   0:01 /usr/bin/python

The console package introduced required the token that is obtained via teamhephy/controller#148

The console is not as reliable as e.g. an ssh client as controls are not passed (e.g. CTR+D, arrow keys etc) and it requires to type exit and hit enter to quit, but it provides a way of accessing the containers without the kubectl superpowers.

[Cryptophobia]

This looks good. See comment in the other PR: teamhephy/controller#148 (comment)

Let me know your thoughts.