fix importing csv with BOM

lib/active_admin_import/model.rb

@@ -77,7 +77,7 @@ def file_path
     def encode_file
       data = File.read(file_path).encode(force_encoding, invalid: :replace, undef: :replace)
       File.open(file_path, 'w') do |f|
-        f.write(data)
+        f.write(data.sub("\xEF\xBB\xBF".force_encoding(force_encoding), "")) # without bom
       end
     end
 

spec/fixtures/files/authors_bom.csv

@@ -0,0 +1,3 @@
+Name,Last name,Birthday
+John,Doe,1986-05-01
+Jane,Roe,1988-11-16

spec/import_spec.rb

@@ -112,6 +112,16 @@ def upload_file!(name, ext='csv')
         end
       end
 
+      context "BOM" do
+
+        it "should import file with many records" do
+          upload_file!(:authors_bom)
+          expect(page).to have_content "Successfully imported 2 authors"
+          expect(Author.count).to eq(2)
+        end
+
+      end
+
       context "with headers" do
 
         it "should import file with many records" do