fix "git fat pull" for fancy named files

just add "-z" to "git ls-files" and split the string at the null byte instead of
newline. now we get the original name back from git and the os module should
handle the communication with the filesystem (but I haven't checked this!).
Merge branch 'pull-with-unicode-filenames' of https://github.com/michaelcontento/git-fat (PR #12)

This does not resolve all unicode file name issues.  We have at least
these issues:

1. Filenames sometimes become command-line arguments, which we'd rather
   avoid because it forces us to decode/encode (on Windows).  This can
   be fixed by systematically using '--stdin' options.

2. We still use 'git ls-files -s' in cmd_index_filter. It should also
   learn to use the -z option, but unfortunately, Python doesn't have
   convenient line processing for NUL-delimited streams so we have to
   write something like difftreez_reader to do that properly.

* 'pull-with-unicode-filenames' of https://github.com/michaelcontento/git-fat:
  fix "git fat pull" for fancy named files

[Normalized quoting style in merge.]