Merge pull request #1478 from okkez/add-log-concat-method

Add `Fluent::Log#<<`

lib/fluent/log.rb

@@ -240,6 +240,9 @@ def puts(msg)
     def write(data)
       @out.write(data)
     end
+    # We need `#<<` method to use this logger class with other
+    # libraries such as aws-sdk
+    alias << write
 
     def flush
       @out.flush

test/test_log.rb

@@ -305,6 +305,10 @@ def test_write
       @log.write("log")
     end
 
+    def test_write_alias
+      assert(@log.respond_to?(:<<))
+    end
+
     def test_out
       assert_equal(@log.out, @logger.out)
       @log.out = Object.new