Allow to configure Engine routes

[fedeagripa]

Actual behaviour

Right now as routes are being added using class_eval there is no configurable way to modify the routes being added (besides re defining the same class_eval yourself in an initializer).

Expected behaviour

Routes could be modified, ideally with except: :delete for example

Related issue

#96

[adamstegman]

This is a good idea! I'll need to do some research on how this could work.