Add deploying from github master using Fabric

This PR allows deployment from github master:

```
fab deploy_app_from_master -H showcase-rps
```

Assuming you have the following ssh config (and your ssh key has been put into ```~ubuntu/.ssh/authorized_keys``` on showcase and the jumpbox):

```
# RPS Jumpbox Configuration
Host jump-rps
     ForwardAgent yes
     User ubuntu
     Hostname 37.26.89.67

Host showcase-rps
     ForwardAgent yes
     User ubuntu
     ProxyCommand ssh jump-rps exec nc -w 9000 192.168.2.3 %p
```

Outstanding work (order or priority):
- Disabling debug mode on showcase
- WSGI mount / deploy the other app (the one for insolvency practitioners)
- Basic auth password protection
- Fabric roles
- Puppetising and documenting ssh key setup