Added form object for adding an "empty" field.
Adding default text for other selection fields.
Merge pull request #27 from wangguan59/empty_selection

Empty selection
Add required fron-end attributes.
Merge pull request #28 from wangguan59/empty_selection

Add required fron-end attributes.
Merge pull request #740 from bcipolli/empty_selection

Replace default selection option