initial mods for our usage of seoserver

- specify PORT and HOST as environment variables
- run phantomjs with --no-images flag for performance gains
- strip <script> tags from responses
- only send Accept: text/html requests to phantomjs, the rest get
  proxied direct to the backend using node-http-proxy
- improved logging, including using express.logger
- improved error handling and SIGTERM handling
- oh yeah, CoffeeScript rewrite