added Kyle S. Goodwin's fix from http://git.io/3zGd-Q

Author: Lester Celestial

lib/grape/api.rb

@@ -386,6 +386,7 @@ def nest(*blocks, &block)
           instance_eval &block if block_given?
           blocks.each{|b| instance_eval &b}
           settings.pop   # when finished, we pop the context
+          reset_validations!
         else
           instance_eval &block
         end

spec/grape/validations/presence_spec.rb

@@ -8,7 +8,7 @@ class API < Grape::API
         default_format :json
 
         resource :bacons do
-          get "/" do
+          get do
             "All the bacon"
           end
         end