Update .gitmodules

[JoshuaWeber]

Url must be to a public available github url. See http://stackoverflow.com/questions/8197089/fatal-error-when-updating-submodule-using-git for more info.

[msftclas]

Hi @JoshuaWeber, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

It looks like you're a Microsoft contributor (Joshua Weber). If you're full-time, we DON'T require a Contribution License Agreement. If you are a vendor, please DO sign the electronic Contribution License Agreement. It will take 2 minutes and there's no faxing! https://cla.microsoft.com.

TTYL, MSBOT;