safety save
update to use latest rev of centos image
remove references to kernel in Instance class
Refactored to move auto-created PD to the DiskMount() object.
back off perf fix and submit via separate pull request
revert to boot=False for backward compatability
after reverting boot arg in DiskMount constructor to default to False,
caller must specify boot=True, when boot PD is desired.
clean up extraneous commented code
update version to default (1) in prep for for pull request
add fixes for upgrading fractal demo to v1 api
revert app version to default (1), not that done testing quick start and fractal
fixes from Brian Dorsey's code review.
minor comment fix
modified to auto-create and auto-delete PDs (simplified from more complex logic that
tried to use pre-created PDs or scratch disk if no existing PD). Now it just assumes
it needs to create the PDs on VM creation and destroy the PDs on VM deletion.
Merge branch 'master' into v1

Conflicts:
	demo-suite/demos/fractal/main.py
Merge pull request #17 from GoogleCloudPlatform/v1

upgrade quick-start and fractal to use gce v1 api