[iOS] Use NSHTTPCookieMaximumAge for version 1 cookies

[aleclarson]

From Apple's documentation:

NSHTTPCookieExpires

An NSDate object or NSString object specifying the expiration date for the cookie.

This cookie attribute is only used for Version 0 cookies. This cookie attribute is optional.

Available in iOS 2.0 and later.

NSHTTPCookieMaximumAge

An NSString object containing an integer value stating how long in seconds the cookie should be kept, at most.

Only valid for Version 1 cookies and later. Default is "0". This cookie attribute is optional.

Available in iOS 2.0 and later.

https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSHTTPCookie_Class/#//apple_ref/doc/constant_group/HTTP_Cookie_Attribute_Keys

[aleclarson]

The offending line: https://github.com/joeferraro/react-native-cookies/blob/master/RNCookieManagerIOS/RNCookieManagerIOS.m#L24

[iegik]

PR are welcome