Update shutil to work with max file path length on Windows

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2016-08-10.23:02:05.599>
labels = ['OS-windows']
title = 'Update shutil to work with max file path length on Windows'
updated_at = <Date 2016-08-12.12:17:45.636>
user = 'https://github.com/brettcannon'

bugs.python.org fields:

activity = <Date 2016-08-12.12:17:45.636>
actor = 'eryksun'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Windows']
creation = <Date 2016-08-10.23:02:05.599>
creator = 'brett.cannon'
dependencies = []
files = []
hgrepos = []
issue_num = 27730
keywords = []
message_count = 5.0
messages = ['272384', '272386', '272405', '272446', '272530']
nosy_count = 6.0
nosy_names = ['brett.cannon', 'paul.moore', 'tim.golden', 'zach.ware', 'eryksun', 'steve.dower']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue27730'
versions = []