+ Added namespace back
 + Create Namespace instance in test
 + Added test case for Namespace::create
 * Clean up include header files
 + Added Namespace::add_subfile
 + Added unit test for Namespace::remove
 + Added unit test for Namespace::add_subfiles()
 - remove full path from struct Metadata
Merge branch 'master' into uni_namespace
 * Extract get_object_id() to a separate function
 + Added Namespace::getattr()
 + Added test case for Namespace::rmdir()
 + Forward declare leveldb store
Merge pull request #29 from vsfs/uni_namespace

Initial work of the unified namespace.
 + Put records into leveldb when create/delete file/dir
 + Added namespace::remove_subfile
 * update persisetn store when add/remove subfile
 * Fixed a typo
 * Initialization
 * Added iterator to TestLevelDBStore
 + Added test case for Namespace::init()
 * Fixed typo
 * Correct comments
Merge pull request #30 from vsfs/store_namespace

Save and Load namespace to/from leveldb