Major changes to donations

- Submission users .serializeArray() instead of plucking params
- New “se_gift” post type, containing basic donor info
- After Stripe completes the payment, we create an se_gift post with
some other info, and save the amount.
- Money format is correct in se_gift Amount column
- Added name and email to donation form
- Fira Sans!
- New landing page for successful donation, with a hash for the URL