Version 0.3.0. Major changes: * added Dir::rename method * optimized FAT access by remembering last allocated cluster (on FAT32 it is also persisted in FSInfo sector) * added proper generation of unique short names * made filesystem struct generic so it is no longer fixed to ReadWriteSeek reference usage * added read_status_flags and stats methods on FileSystem for getting general information about volume * added FileSystem::unmount method for safe unmounting * added no_std support