Add: first homework project of Advanced OS
Fix: free_netdev called twice

This device defines a destructor to `free_netdev`, which conflict with
the module's exit code (a device will be freed twice)

Not sure if this is a good fix. What if a kernel module can generate
serveral devices like the `tun` module? Should we free the device using
destructor, or using module's exit function?
Merge branch 'master' of github.com:yegle/homework-code-at-uga

Conflicts:
	spring2013/csci8730-advanced-operating-system/01-fix-kernel-module/netdev.c