+ defined fd to obj interfaces in VsfsFuse
* implmentation
Merge branch 'master' of github.com:vsfs/vsfs into vsfs_fuse_ops
* changed storage_manager::open to return ptr
 + Make FUSE functional
 * Fixed the bug that can not remove file from parent directory.
 + Added a unit test to verify the above bug
 * Check the existence of files on the base directory after deleting the
 files from vsfs-FUSE
Merge pull request #60 from vsfs/vsfs_fuse_ops

Raw IO in FUSE