currency can be null
Add 3 more missing fields

This adds:

* name to #stripe_card
* trial_start and trial_end to #stripe_subsciprtion
properly decode discounts and coupons
Currentcy -> Currency in Coupon record
Remove 'nine' and replace with non-counting words
Bump to version 0.6.3

This includes:
  • name added to card record
  • trial_{start,end} added to subscription
  • decode discount and coupon records

Records have changed in this version, so recompiles all around.

All 12 tests pass.
Merge branch 'v1' of git://github.com/mattsta/stripe-erlang into v1

Conflicts:
	include/stripe.hrl
	src/stripe.erl