Fixes #10497: Fix Windows 8 and Windows Phone 8 behavior and apply to docs

Per #10497 (closed), some things for Windows 8, Windows Phone 8, and Internet Explorer 10 are not what they seem. This pull request fixes a few things up around that:

• Drops the global @ms-viewport usage that was causing Windows Phone 8 devices to display scaled down versions of a "desktop site"
• Clarifies the docs in the Browser Support section on the Getting Started page to provide additional context
• Applies the fix to the docs so folks have an example to pull from if need be.

/cc @cvrebert @laurentperez