[compute/google] Upgrade GCE to v1beta15 and fix a bunch of bugs

This isn't quite ready to merge, but I wanna put it out there. 

Two questions I have for @geemus and team:

1) Right now I'm just printing out errors I'm getting in responses. What's the best way to deal with errors in fog?

2) I've just been using p for debugging and the like, is there an official Fog logger? I haven't been able to find one (this might be the answer to 1).