proposal for windows unicode

[sonoro1234]

After dicussion in PR #57 my proposal would be to wrap all functions in lfs taking a path so that it is converted to unicode. Functions that return paths would convert them from unicode to UTF-8.

In order to keep compability io.open and other Lua functions taking paths would be overloaded by functions from lfs (lfs.open lfs.remove) so that would be lfs 1.8 (instead of 2.0)

[sonoro1234]

Doing a test to check size of all a directory tree I could measure the speed of https://github.com/luapower/fs against luafilesystem and https://github.com/sonoro1234/luafilesystem:

It took arround 36 seconds for both lfs and 8 seconds for fs.
It is unicode aware (providing functions for opening files, etc ) and has a different directory iterator providing filename and a fileinfo object.

This fileinfo object is the key to speed (as I could check making a lfs_ffi.lua version of it): you can avoid calling lfs.attributes which is the main cause of the slow performance.
implemented for win32 only by now in https://github.com/sonoro1234/luafilesystem branch newiterator

I think that future versions of lfs should take a look at https://github.com/luapower/fs