Changed Procfile target and database connections

Hi Hendrik,

I needed to change two files for my dokku deployment of #pants.

## the Procfile.
dokku has some default process types for rails applications:
```
-----> Discovering process types
       Procfile declares types -> web
       Default process types for Ruby -> rake, console, web, worker
```

If the Procfile defines "pants" as a Process type, the app won't start. This is, why I changed it to "web".

## Database configuration
My database username is not pants, neither is my database name pants_production. Having full control over database.yml with environment parameters simplified the dokku deployment.

With those two changes, pants deployments with dokku will work out of the box.

Cheers
Dennis