Format fails when directories contain spaces.

Windows 10:

Command failed: C:\Windows\system32\cmd.exe /s /c "yapf c:\tmp dir\test.py"
yapf: Input filenames did not match any python files

Ubuntu 14.04:

Command failed: /bin/sh -c autopep8 /vagrant/tmp dir/test.py
usage: autopep8 [-h] [--version] [-v] [-d] [-i] [--global-config filename]
[--ignore-local-config] [-r] [-j n] [-p n] [-a]
[--experimental] [--exclude globs] [--list-fixes]
[--ignore errors] [--select errors] [--max-line-length n]
[--line-range line line]
[files [files ...]]
autopep8: error: autopep8 only takes one filename as argument unless the "--in-place" or "--diff" args are used

Tested this branch in both OS's listed above.