Fixed a bug in the _ajax method. It used to set timeout even if async = true.
Although this used to work it is apparently standard behaviour to fail in this case
(see http://www.w3.org/TR/XMLHttpRequest/#the-timeout-attribute) and this recently started failing.
Personally I think this is a very stupid limitation.
Apparently this limitation is only in effect in a "document environment", and Xmla tries to verify
that condition so that other environments (node) are not affected by this silly design mistak.
I assume my test for "document environment" (window && window.document) can be improved.
Please let me know if that is the case.
See previous commit.