Adds Automatic Support to Not Use Multipart Uploads If File Size <= partSize

[bikeath1337]

Thanks to @jakubzitny for #362.

This PR has not be tested yet, but specs pass (I will remove the WIP after doing more testing).

What this intends to do: Enhance Evaporate to avoid the overhead of using multipart uploads if the file size is equal to the part size. This option avoids two round trips to AWS (initiate and complete).

Description:

• The feature is enabled by default. To disable, use the provided option enablePartSizeOptimization
• The started, progress and complete callbacks should all be invoked
• computeContentMd5 should be respected
• Retry features should be maintained

Changes:

• The complete callback's xhr parameter will be undefined.

[jakubzitny]

Hey @bikeath1337, so I found some time to try this out and plugged this branch into our code. However I am getting SignatureDoesNotMatch errors. Not sure if there are some differences in auth when using Multipart or this simple PUT API. We're using the customAuthMethod for signing requests.

I'll try a simpler example to see if that works.

EDIT: Yeah I seem to be getting the same for the simple example. Let me dig into it some other time again 😛

[bikeath1337]

Hi, @jakubzitny , I'm back from being away... :) Any update on this?