Allow XMLHttpRequest to be mocked by test frameworks (e.g., jasmine-ajax; sinon)

[cacieprins]

Currently the local xhrHttp is defined at require-time.

Unfortunately, libraries for mocking out XMLHttpRequests that rely on replacing global.XMLHttpRequest with a mock do not play nicely with this - you've already gained a reference to the real XMLHttpRequest by the time they replace the global.XMLHttpRequest reference.

Will be submitting a pull request to fix.

[jednano]

Any progress on this @jonprins?

[cacieprins]

My pull request is being ignored :(

I may clean it up and re-submit.