Merge remote-tracking branch 'origin/master' into gsmendoza/92-merge-…

…solidus-paypal-braintree

Resolves #92.

Implemented with

```
git remote add solidus_paypal_braintree git@github.com:solidusio/solidus_paypal_braintree.git
git reset --hard solidus_paypal_braintree/master
git merge origin/master --strategy ours --allow-unrelated-histories
```