Added a method to AjaxException to check for timeout status.

[ochrons]

As XHR doesn't offer a clear status for indicating timeout, this method provides an easier way to check for timeout. Tried also using ontimeout but it gets called after onreadystatechange making it rather useless in this case.

Change-Id: Ia0d66bd4ca27f2ce0157258bcc885817efe21a2f

[sjrd]

I'd rather this method be called isTimeout.

[sjrd]

Is there some spec somewhere backing the assumption about these status and readyState?

[sjrd]

Also, wouldn't it be more appropriate to identity timeouts right where the AjaxException is created, and throw a scala.concurrent.TimeoutException instead?

[ochrons]

scala.concurrent.TimeoutException would be ok, but breaks backwards compatibility with code that expects to receive an AjaxException.

Couldn't find any explicit spec on how to detect timeout (except with ontimeout), but that combination of status values seemed to be used elsewhere (for example #37)

[ochrons]

Tested this on Chrome, Firefox and IE11 and the timeout detection works ok on all of them.

[sjrd]

OK, I guess that makes sense this way, then. I'd still like it to be called isTimeout, to follow Scala's sort-of conventions.

[ochrons]

Since I messed up my fork branching and cannot squash these commits, gonna close this PR and redo it The Right Way