Fix some errors on shoulda's matchers

lib/paperclip/matchers/validate_attachment_presence_matcher.rb

@@ -39,14 +39,14 @@ module Paperclip
         def error_when_not_valid?
           @subject.send(@attachment_name).assign(nil)
           @subject.valid?
-          not @subject.errors[:"#{@attachment_name}_file_name"].blank?
+          @subject.errors[:"#{@attachment_name}"].present?
         end
 
         def no_error_when_valid?
           @file = StringIO.new(".")
           @subject.send(@attachment_name).assign(@file)
           @subject.valid?
-          @subject.errors[:"#{@attachment_name}_file_name"].blank?
+          @subject.errors[:"#{@attachment_name}"].blank?
         end
       end
     end

lib/paperclip/matchers/validate_attachment_size_matcher.rb

@@ -18,7 +18,6 @@ module Paperclip
       class ValidateAttachmentSizeMatcher
         def initialize attachment_name
           @attachment_name = attachment_name
-          @low, @high = 0, (1.0/0)
         end
 
         def less_than size
@@ -76,21 +75,19 @@ module Paperclip
         end
 
         def lower_than_low?
-          not passes_validation_with_size(@low - 1)
+          @low.nil? || !passes_validation_with_size(@low - 1)
         end
 
         def higher_than_low?
-          passes_validation_with_size(@low + 1)
+          @low.nil? || passes_validation_with_size(@low + 1)
         end
 
         def lower_than_high?
-          return true if @high == (1.0/0)
-          passes_validation_with_size(@high - 1)
+          @high.nil? || @high == Float::INFINITY || passes_validation_with_size(@high - 1)
         end
 
         def higher_than_high?
-          return true if @high == (1.0/0)
-          not passes_validation_with_size(@high + 1)
+          @high.nil? || @high == Float::INFINITY || !passes_validation_with_size(@high + 1)
         end
       end
     end