Makes Fog::Collection rubocop compliant

 * Refactored inspect method into a few composed methods, within a new module. This takes care of the ABC level being too high in Fog::Collection.inspect, and gets the class definition down to 100 lines. 

 * The names of the module where the new methods reside and  methods themselves obviously need to be though out and renamed to something meaningful ( add_stuff() is definitely not a good name : p )

 Also, I don't like the way each method depends on having a block provided it to instead of the data, however I was trying to avoid too many LOC and assignments. Long story short, right now not entirely happy with the new module, but it's a start.
Sure. The actual `Collection` model depend on a real connection to work so i think one solution to test it is overwrite some methods to work on top of it without a real connection like [here](https://github.com/fog/fog-core/blob/master/spec/fog_attribute_spec.rb#L4-L62). I know it sound bad but was the easier solution i found.