Add `/browserconfig.xml` and tile images

By default, starting with IE11 on Windows 8.1, IE will request the `/browserconfig.xml` file when a user clicks/touches the `pin site` button  <img src="https://f.cloud.github.com/assets/1223565/1736715/6bd969f6-6367-11e3-8b00-3bc09f01c5f5.png" width=20 height=20> (same as Safari for iOS does with the `apple-touch-icons` when the user touches the `share` button <img src="https://f.cloud.github.com/assets/1223565/1736738/c43f0f60-6367-11e3-9431-30abd9441bf7.png" width=20 height=20> ).

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![](https://f.cloud.github.com/assets/1223565/1751261/34f6eb58-65d7-11e3-89a2-08c7f33fb756.png)
_How tiles look like_

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Adding `/browserconfig.xml` and the tile images:

* reduces the number of 404s, especially as IE11 on Windows 8.1 gets more market share
* provides a starting point for dealing with Windows tiles
* reminds users about the tile images, so that their website doesn't end up having as a tile the default IE11 logo, or (if the favicon is 32×32px or bigger and not `.ico`) the website's favicon
* unlike using `<meta>` tags, offers a way that doesn't increase the page size

Only two images are provided since:

* `tile.png` (558×558px) - can be used for the `Small`, `Medium`, and `Large` tiles, being automatically resized where necessary
* `tile-wide.png` (558×270px) - can be used for the `Wide` tile as, in this case, resizing the 558×558px image would just end up looking weird
    
The two images are 558×558px and 558×270px because those are the recommended image sizes in order for the tiles to look good on a wide range of devices.

For more in depth information, please refer to the MSDN documentation:
* http://msdn.microsoft.com/en-us/library/ie/dn455106.aspx
* http://msdn.microsoft.com/en-us/library/ie/dn255024.aspx

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Note(s): 

* from my tests, the `/browserconfig.xml` file seems to be requested even if the tile images are specified in the `html` page:

  ```html
<meta name="msapplication-TileColor" content="#000"/>
<meta name="msapplication-square70x70logo" content="tiny.png"/>
<meta name="msapplication-square150x150logo" content="square.png"/>
<meta name="msapplication-wide310x150logo" content="wide.png"/>
<meta name="msapplication-square310x310logo" content="large.png"/>
```