Using a different base image and disabling StrictHostKeyChecking

This works great for me in my vagrant/coreos setup:

```
core@core-01 ~ $ docker run -t -v /home/core/.ssh:/keys -i 0e36556558a8
Agent pid 11
Identity added: /keys/id_rsa (/keys/id_rsa)
Key added... testing github connection...
Warning: Permanently added 'github.com,192.30.252.130' (RSA) to the list of known hosts.
Hi oxtopus! You've successfully authenticated, but GitHub does not provide shell access.
```