fix case sensitivity in sis headers

test plan:
 * import a csv file with all-caps headers
 * it should still work

Change-Id: Ifeac18095e742e974f3709915d6d21f8c5d2d11a
Reviewed-on: https://gerrit.instructure.com/11206
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Cody Cutrer <cody@instructure.com>

lib/sis/csv/import.rb

@@ -397,6 +397,7 @@ module SIS
           end
           begin
             FasterCSV.foreach(csv[:fullpath], BaseImporter::PARSE_ARGS.merge(:headers => false)) do |row|
+              row.each(&:downcase!)
               importer = IMPORTERS.index do |importer|
                 if SIS::CSV.const_get(importer.to_s.camelcase + 'Importer').send('is_' + importer.to_s + '_csv?', row)
                   @csvs[importer] << csv

spec/lib/sis/csv/account_importer_spec.rb

@@ -140,4 +140,18 @@ describe SIS::CSV::AccountImporter do
     Account.find_by_sis_source_id('A001').name.should == "Science"
   end
 
+  it 'should match headers case-insensitively' do
+    before_count = Account.count
+    process_csv_data_cleanly(
+      "Account_ID,Parent_Account_ID,Name,Status",
+      "A001,,Humanities,active"
+    )
+    Account.count.should == before_count + 1
+
+    a1 = @account.sub_accounts.find_by_sis_source_id('A001')
+    a1.should_not be_nil
+    a1.parent_account_id.should == @account.id
+    a1.root_account_id.should == @account.id
+    a1.name.should == 'Humanities'
+  end
 end