Github::Request#request fails when fails when params are a hash

Not sure if this is the cleanest approach, but just wanted to start a dialog and this works.

How to reproduce:

```
[36] pry(main)* Github::API.new.ratelimit
EXECUTED: get - /rate_limit with PARAMS: {}
NoMethodError: undefined method `options' for {}:Hash
from /Users/phil/Development/rbsavvy/gistr/.bundle/ruby/2.0.0/gems/github_api-0.10.1/lib/github_api/request.rb:38:in `request'
```