Add btrfs-tools in the helper's packages list
Update the helper kernel to 3.14.15

Newer kernels work better with btrfs
Don't fail if /etc/fstab is missing

If /etc/fstab is missing do not mount any other partition than the
root partition but do not fail. There are distros like CoreOS that
do not contain an `/etc/fstab'.
Preserve the name when resizing GPT partitions
Detect CoreOS in get_base_distro()
Allow mounting btrfs file systems in mount_all()
Support enlarging btrfs file systems

Resizing of a btrfs file system is performed in FilesystemResizeMounted
configuration task.
Merge pull request #61 from skalkoto/feature-coreos-support

Support for CoreOS Linux