Microsoft has started sharing its Windows Phone 8.1 Software Development Kit (SDK) with developers, and the inevitable leaks have begun. Over on Reddit, one developer is documenting all of the updates discovered in the Windows Phone 8.1 SDK. The first significant change appears to be the initial signs of a Windows Phone and Windows RT merger. Microsoft has been hinting at this plan, and the SDK includes Universal App support with templates to build Windows Store and Windows Phone Store apps from the same shared HTML and JavaScript code. While it’s not clear how easier it is to create apps that run across both tablets and phones, the inclusion of this support suggests that’s a big focus for Microsoft with this update.