Return XPath integers as actual integers.

This is to ensure that calls such as string(10) return "10" and not "10.0". It
also saves integer -> float conversions when they're not needed.

lib/oga/xpath/evaluator.rb

@@ -794,7 +794,7 @@ module Oga
       # @return [Float]
       #
       def on_int(ast_node, context)
-        return ast_node.children[0].to_f
+        return ast_node.children[0]
       end
 
       ##

spec/oga/xpath/evaluator/calls/string_spec.rb

@@ -37,7 +37,7 @@ describe Oga::XPath::Evaluator do
       end
 
       example 'convert an integer to a string' do
-        @evaluator.evaluate('string(10)').should == '10.0'
+        @evaluator.evaluate('string(10)').should == '10'
       end
 
       example 'convert a float to a string' do

spec/oga/xpath/evaluator/types/int_spec.rb

@@ -12,8 +12,8 @@ describe Oga::XPath::Evaluator do
       @number.should == 1
     end
 
-    example 'return integers as floats' do
-      @number.is_a?(Float).should == true
+    example 'return integers as Fixnums' do
+      @number.is_a?(Fixnum).should == true
     end
   end
 end