EasyPost/easypost-ruby — pull request #15 by deeeki (2014-09-15 22:26:48+00:00)
Title: Enable `Shipment#lowest_rate` to handle nil argument

to prevent the following case.

```
Failure/Error: rate = @shipment.lowest_rate(nil, 'Express')
NoMethodError:
undefined method `split' for nil:NilClass
```