Merge pull request #1 from zhangsl16/Helen-Working

Helen working
Merge branch 'master' of https://github.com/zhangsl16/compositefs into Helen-Working
Merge pull request #2 from zhangsl16/Helen-Working

Helen working
Merge branch 'master' of https://github.com/zhangsl16/compositefs into Helen-Working
ls -l now shows proper file size for composit files (via getattr), added helpers get_file_end and get_file_begin
removed extraneous commented code, added comments