Add hping to the ramdisk. Also, do some very simple versioning.

Add hping to the ramdisk.  Also, do some very simple versioning.
This is the first change to the ramdisk since v0.1.0.  So, we now build
the image as initrd-X.Y.img, and link initrd.img to it.  This lets us
have a few checks to make sure that people rebuild their ramdisks when
necessary.