add storage server count
Add file fault tolerance, any time, at least 2 file copies in the
system!
ls function improvement
add a slash / in front of the directory
Add new file implement fault tolerance with 2 copies
Optimize getStorage method to return a available storage based on fault
tolerance
implement add for fault tolerance
minor fix for mkdir
refactor naming service
fix put
refactor naming server
done with put
done with append
done with random read and random write
make append to be shown for lock
add demo files