CSV.read: Add support for integer mode again

Fix GH-336

Reported by Dave Burgess. Thanks!!!

Author: kou

lib/csv.rb

@@ -1976,7 +1976,7 @@ def may_enable_bom_detection_automatically(filename_or_io,
       return unless Encoding.default_external == Encoding::UTF_8
       return if options.key?(:encoding)
       return if options.key?(:external_encoding)
-      return if mode.include?(":")
+      return if mode.is_a?(String) and mode.include?(":")
       file_opts[:encoding] = "bom|utf-8"
     end
 

test/csv/interface/test_read.rb

@@ -112,6 +112,12 @@ def test_open_block_return_value
     assert_equal("Return value.", return_value)
   end
 
+  def test_open_mode_integer
+    CSV.open(@input.path, File::RDONLY, col_sep: "\t") do |csv|
+      assert_equal(@rows, csv.read)
+    end
+  end
+
   def test_open_encoding_valid
     # U+1F600 GRINNING FACE
     # U+1F601 GRINNING FACE WITH SMILING EYES