[Validator] Update validator for new Linter::Results class

Updates for https://github.com/CocoaPods/Core/pull/131.

Gemfile.lock

@@ -7,7 +7,7 @@ GIT
 
 GIT
   remote: https://github.com/CocoaPods/Core.git
-  revision: ce564c47d0b499d004c156857ac6e6d8b74024ae
+  revision: 54010ab5adb9e323d0c287089504115847c20d36
   branch: master
   specs:
     cocoapods-core (0.34.4)

lib/cocoapods/validator.rb

@@ -192,7 +192,7 @@ module Pod
     #
     def perform_linting
       linter.lint
-      @results.concat(linter.results)
+      @results.concat(linter.results.to_a)
     end
 
     # Perform analysis for a given spec (or subspec)
@@ -401,7 +401,7 @@ module Pod
 
     # Specialized Result to support subspecs aggregation
     #
-    class Result < Specification::Linter::Result
+    class Result < Specification::Linter::Results::Result
       def initialize(type, message)
         super(type, message)
         @subspecs = []