Adds ability to exclude count from results

[davbre]

This relates to issue 13. You can exclude counts from results in the following ways:

class WidgetPresenter < Brainstem::Presenter
  presents "Widget"

  #1. exclude the count and do not allow counts to be requested
  exclude_count

  #2. exclude the count and allow counts to be requested in url, e.g. with "count=true"
  exclude_count allow: true


(etc)

end

If the exclude_count method is not used in the presenter definition, the count can be excluded using "count=false" in the url query string.

If you've any questions, just let me know. And by the way, nice gem :)

[cantino]

Hey @ivadnerb, thanks for the contribution! I'm at RailsConf right now, but I'll dig into this when I get back.

[cantino]

Brainstem still needs to support 1.9, so kwargs can't be used quite yet unfortunately.