[WIP] Wizard apply

- [ ] show confirmation message after each step.
- [ ] combine new api key and new marketplace form into one (or use two different routes)
- [ ] implement modal with deep linking
- [ ] update CSS
- [ ] add api key confirmation modal
there's a discrepancy about what accept header to use.

from [the docs](https://docs.balancedpayments.com/1.1/api/bank-accounts/#fetch-a-bank-account) we have `"Accept: application/vnd.api+json;revision=1.1"` looks like the [api spec](https://github.com/balanced/balanced-api/blob/master/features/support/initial_setup.rb#L6) uses that too.

i guess it doesn't make a difference either way!