Drop-in Chooser on Windows Phone 8.1

Hi,

Well, my proposel is that the Dropbox Chooser already works on Windows Phone 8.1, except the Dropbox.isBrowserSupported() function prevents it from working.

In visual studio I can start a IE debug session on Windows Phone, if I Then replace the Dropbox.isBrowserSupported() function by :

function() { return true; }

The dropbox file chooser works as expected.

So my proposel would be to finetune the isBrowserSupported function to enable Windows Phone 8.1,
useragents for IE11 on Windows Phone 8.1 can be found here https://msdn.microsoft.com/en-us/library/ie/hh869301(v=vs.85).aspx