google github library returns *Foo in singular case and []Foo if there
are many results. seems like the best approach is to pass them around
by-value, since *Foo seems to only be so that they can return 'nil'
instead of a zero-value.
* fix some err checks
* github api url can be configured (e.g. point it at an enterprise instance)
[finishes #89638752#89633744]
Signed-off-by: Chris Brown <cbrown@pivotal.io>
