Log Message:
py-fakefs: updated to 3.6

Version 3.6:

Changes
* removed unneeded parameter use_dynamic_patch

New Features
* support for src_dir_fd and dst_dir_fd arguments in os.rename,
  os.replace and os.link
* added possibility to use modules instead of module names for the
  additional_skip_names argument
* added argument allow_root_user to Patcher and UnitTest to allow
  forcing non-root access
* added basic support for os.pipe
* added support for symlinks in add_real_directory
* added new public method add_real_symlink

Infrastructure
* added check for correctly installed Python 3 version in Travis.CI

Fixes
* fixed incorrect argument names for some os functions
* fake DirEntry now implements os.PathLike in Python >= 3.6
* fixed incorrect argument name for os.makedirs
* avoid pytest warning under Python 2.7
* add __next__ to FakeFileWrapper