Allow to provide parameters for PullRequests list

According to the [API documentation](https://developer.github.com/v3/pulls/#list-pull-requests) of the v3 API a sort can be added and some other parameters not yet supported by this library. I have changed the "all" function to allow parameters to be given.
Fix tests and add defaults
Also fix the actual tests since it requires an array now
Tabs vs spaces, missing )
Merge pull request #136 from syphernl/patch-1

Allow to provide parameters for PullRequests list