package: update "debug" to v2.0.0
package: update "debug" to v2.1.0
examples: add "progress" listeners to upload example
progress point...
examples: multiply percent complete by 100
index: refactor to not use Promise anymore

Now firing "load" and "error" events directly on
XHR instance that gets returned to the user.

Backwards comapt is supported for the callback API,
but treating the response like a Promise no longer works
as expected.
examples: tweak "me.html" example since it no longer returns a Promise
package: remove unused "promise" dependency
examples: tweak `console.log()` call
Merge pull request #4 from Automattic/add/progress-events

Return an XMLHttpRequest instance, add support for "progress" events