Rewind IO input upon resetting the lexer.

lib/oga/xml/lexer.rb

@@ -91,6 +91,8 @@ module Oga
         @line     = 1
         @elements = []
 
+        @data.rewind if io_input?
+
         reset_native
       end
 

spec/oga/xml/lexer/io_spec.rb

@@ -15,5 +15,12 @@ describe Oga::XML::Lexer do
         [:T_ELEM_END, nil, 2]
       ]
     end
+
+    example 'rewind input when resetting the lexer' do
+      lexer = described_class.new(StringIO.new(('<a>foo</a>')))
+
+      lexer.lex.empty?.should == false
+      lexer.lex.empty?.should == false
+    end
   end
 end