Proper handling of decimals for string() calls.

When calling the string() XPath function floats with zero decimals (10.0, 5.0,
etc) should result in a string without any decimals. Ruby converts 10.0 to
"10.0" whereas XPath expects "10".

lib/oga/xpath/evaluator.rb

@@ -784,6 +784,13 @@ module Oga
         if convert.respond_to?(:text)
           return convert.text
         else
+          # If we have a number that has a zero decimal (e.g. 10.0) we want to
+          # get rid of that decimal. For this we'll first convert the number to
+          # an integer.
+          if convert.is_a?(Float) and convert.modulo(1).zero?
+            convert = convert.to_i
+          end
+
           return convert.to_s
         end
       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