cookies.morsel_to_cookie morsel['expires'] can't be strtime, and morsel['max-age'] convert to expires problem repair

eg. view yahoo.com will return:
```
Set-Cookie	B=9a3jpi98r1dd8&b=3&s=fb; expires=Sun, 07-Jun-2015 16:15:36 GMT; path=/; domain=.yahoo.com
```

expires is str time, but cookielib.Cookie.expires only int
py code:
```
    str_cookie = "B=9a3jpi98r1dd8&b=3&s=fb; expires=Sun, 07-Jun-2015 16:15:36 GMT; path=/; domain=.yahoo.com"
    C = Cookie.SimpleCookie(str_cookie)
    for morsel in C.values():
        cookie = requests.cookies.morsel_to_cookie(morsel)
        print cookie
```