filter() doesn't return a list in Python 3
ensure Python 2 compatibility with filter() using itertools.ifilter
Merge pull request #37 from esistgut/patch-1

filter() doesn't return a list in Python 3
Update README.md
Disallow to send empty payment description
Merge pull request #39 from mirumee/features/required-payment-description

Disallow to send empty payment description
Stripe payment: Invalid integer

self.payment.total doesn't return an integer so ../stripe/api_requestor.py returns an error
Merge pull request #40 from sergiobrr/master

Stripe payment: Invalid integer
Merge branch 'master' into preauth

Conflicts:
	payments/paypal/__init__.py