Github Plugin: `perpage` parameter to `per_page`
Github Plugin: `perpage` parameter to `per_page`

I'm guessing that at some point the Github API changed the "per page"
parameter from `perpage` to `per_page`. This code change makes sure that
we are up to date with the Github API.

- [Github API Pagination](https://developer.github.com/v3/#pagination)

jiusanzhou/dillinger,joemccann/dillinger,benjamin-albert/dillinger,benjamin-albert/dillinger,jiusanzhou/dillinger,joemccann/dillinger,joemccann/dillinger,jiusanzhou/dillinger