Merge branch 'new-signup-add-credit-card'

* new-signup-add-credit-card:
  Happy path for credit card signup
  Panic should work on any value for error
  Allow getting default payment method, not just index
  Object representing the backend SGX to use
  Stop polluting Object namespace with Blather DSL
  Work in the presence of em-synchrony
  Helper to allow ordering phone number from Bandwidth v2
  Helper to get a promise that resolves after N seconds
  Every payment kind will need the plan, so put it at the top
  Use registration pattern for Payment kinds
  Method to bill the plan of a Customer
  Use Forwardable for simple delegations
  Helper to allow using sync-style code in a Promise context
  New signup: go to web to choose credit card
  OOB helper
  Reject promise on stanza error
  Fix typo

Helper to allow ordering phone number from Bandwidth v2

Uses their gem which uses Faraday. Set Faraday to em-synchrony so their gem is
now using EventMachine but still sync so their code will work unchanged.  Wrap
all uses of the gem in EM.promise_fiber to get a promise back out of that.

Implement a poll helper that can wait until a new order is complete at Bandwidth
before continuing.  They support an HTTP callback method, but only global on
account? This is much easier to work with in our context.