Marathon 0.5.1 support with haproxy

So, I'm new to the whole ansible thing but I wanted to share this update to the ansible-marathon playbook. It takes a different approach which worked better for me:

- Uses pre-built marathon distributrion from mesosphere, so no need to compile
- Adds haproxy support (requires haproxy) so you can have haproxy route to marathon instances using a wild-card sub-domain.