2.7 stub updates (#149)

* Stubgen modules for 2.7

Cookie
email._parseaddr
email.utils
genericpath
linecache
mimetypes
multiprocessing
multiprocessing.process
multiprocessing.util
posixpath
quopri
runpy
weakref
wsgiref.validate

* 2.7/typing.py: add missing __contains__ definition

* 2.7/subprocess.py: make output argument to CalledProcessError optional

Commit f08160bd did the same for py3.

* 2.7/hmac.pyi: add compare_digest

This function was introduced to the 2.7 series in 2.7.7.

* Stubgen 2.7/ssl.pyi

This replaces a nearly-empty handwritten stub.

* Copy constants and other definitions from py3 to py2 ssl.pyi

* 2.7/__future__.pyi: add methods

* 2.7/_weakref.pyi: backport some definitions from 3.x version

* Stubgen 2.7/locale.pyi

Hand-edited to remove declarations that are redundant (and cause
conflicts with) the "from _locale import *" line.

stdlib/2.7/subprocess.pyi

@@ -29,7 +29,7 @@ class CalledProcessError(Exception):
     cmd = ...  # type: str
     output = ...  # type: str # May be None
 
-    def __init__(self, returncode: int, cmd: str, output: str) -> None: ...
+    def __init__(self, returncode: int, cmd: str, output: str = ...) -> None: ...
 
 class Popen:
     stdin = ... # type: Optional[IO[Any]]