test,util/packer: Use tup ppa from titanous and suid root

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
all: Run go builds in a chroot

This ensures that all dependencies in the tree are tracked by tup.

Depends on gittup/tup#201 and
https://codereview.appspot.com/141840043/

Closes #199

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
Merge pull request #374 from flynn/chroot-build

Chroot build