Timeout library sets status code to 0

[Allcharles]

Timeout library sets the status code of timed out requests to 0. This may cause issues for a number of people because of the following:

• 0 is a boolean value for false and may interfere with pre-existing logic as no other code will return falsy
• There is no clear documentation saying what the status code will be (my first assumption was either a 408 Request Timeout, or 504 Gateway Timeout)

It would be nice if we either used an existing status code, or allow the status code to be set by the user in the forRoot so that they can prevent the use of magic numbers in their application.

[IKatsuba]

@Allcharles, thank you for the excellent issue! I will try to think about that