Feat/evap upload svc

* made some small improvements to evaporate provider.
* added some meat to the upload service.
* added some basic tests for upload service, other parts of upload not yet tested.
* use of uuid and env in prefixing upload file name
* additional headers for content type, disposition, and privacy
Do you think it's worth adding a `then` method to the Upload prototype that just does: `this.promise.then.apply(this.promise, arguments)`? Might be a nice shorthand.