Reverts non-fix connection issues

Our connection issues were due to a naming mismatch (`UNICORN_WEB_WORKERS` in the Unicorn config, `ROUTEMASTER_WEB_WORKERS` on the staging environments).

Besides (pointer to @nas since I misled him), using a class variable in the `Bunny` mixin _does_ mean a single connection is used for the whole process. Read [here](http://blog.codegram.com/2011/4/understanding-class-instance-variables-in-ruby), or [here](http://blog.elliottcable.name/posts/mixins_and_class_variables.xhtml). It's easy to test yourself, too :smile_cat: 

This also closes #20.