v1.7.1

This release provides early access for ordering the rootfs based on the OTP init
script's primload order. With this feature, one can order .beam files
contiguously rather than distributed across the file system. This can be a boot
performance optimization on systems with slow I/O since it allows for reads from
the device to pull in multiple .beam files into memory at a time. It requires
corresponding updates to nerves to pass in the order.