Add warnings to the installer about running crouton from a TTY.
Support using arbitrary archives as bootstrap files.

This means you can tar up an existing chroot and then "install" it via the
installer script.
Add X11-less chroot tip to tips.
Remount /tmp with exec for consistency.
Add syncs to unmount-chroot to avoid dataloss if umount explodes.

It appears that ecryptfs unmount can be unstable if there are large amounts of
stuff to commit. Syncing before and after just helps avoid the problem.
Add sanity check if the mount-chroot script is empty.
Skip mount helpers when remounting.
Add exec to the chroot /tmp, not the host /tmp.
Add support for custom target files via the -T parameter.
Add compile function to prepare script for precompiling executables.

This allows crouton to remove compile-time packages once they're no longer
needed. Precompile croutonticks for croutonpowerd using this method.
Short-circuit passwd queries.
Make GID management smart, and handle changes when Chromium OS is updated.

Critical GIDs are now set to match Chromium OS on each enter-chroot.
This is because the group GIDs can change between releases, since the entire
rootfs gets swapped. There has been at least one instance of someone not having
video acceleration due to different GIDs.
Add a partially-generated version number to the installer.