godash: adjust to breaking upstream change
godash: adjust to breaking upstream change

Package github.com/google/go-github/github introduced some breaking
changes (changing Issue to *Issue and Milestone to *Milestone in some
return values).

Change-Id: I0eceb6247194fd2f27fe629dbdf70509e03ba86b
Reviewed-on: https://go-review.googlesource.com/25463
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build