Merge pull request #1 from octabrain/master

Replace spaces with tab in Makefile
Merge pull request #3 from octabrain/master

Add filesystem superblock and directory layout
corrected typo in testfs_dir_entry
added dir.c and file.c
block size changed to 4096
added dir.o and file.o
added incomplete read_inode function
Read block size and check magic number from superblock