Add setup.py

This makes ansible-lint packageable so it can be pip installed and what not.

```
$ mkvirtualenv ansible-lint
New python executable in ansible-lint/bin/python
Installing setuptools, pip...done.

$ pip install ~/dev/git-repos/ansible-lint
...
Successfully installed ansible ansiblelint paramiko jinja2 PyYAML pycrypto ecdsa markupsafe
Cleaning up...

$ ansible-lint ~/dev/surveymonkey/smstack/vagrant.yml
[ANSIBLE0008] Tasks must have tag
/Users/marca/dev/surveymonkey/smstack/roles/vagrant/tasks/main.yml:0
{'with_file': ['../../../authorized_keys'], 'authorized_key': 'user={{user}} key="{{item}}" state=present', 'name': 'Set up authorized_keys for the user "{{user}}"'}

[ANSIBLE0008] Tasks must have tag
/Users/marca/dev/surveymonkey/smstack/roles/vagrant/tasks/main.yml:0
{'copy': "src='../../../files/ssh_config' dest='/home/{{user}}/.ssh/config' mode=600", 'name': 'copy the ssh config over'}

[ANSIBLE0008] Tasks must have tag
/Users/marca/dev/surveymonkey/smstack/roles/dev/handlers/main.yml:0
{'sudo': True, 'command': 'supervisorctl reload', 'name': 'restart supervisor'}
...
```

Cc: @sontek, @aconrad