Change gh-page URLs to use .io

GitHub have redirected all `username.github.com` pages to
`username.github.io`.

README.md

@@ -5,15 +5,15 @@ elements more consistently and in line with modern standards. We researched the
 differences between default browser styles in order to precisely target only
 the styles that need normalizing.
 
-[Check out the demo](http://necolas.github.com/normalize.css/2.1.0/test.html)
+[Check out the demo](http://necolas.github.io/normalize.css/2.1.0/test.html)
 
 [Legacy browser support is available in v1](https://github.com/necolas/normalize.css/tree/v1)
 
 ## Install
 
-Download from the [project page](http://necolas.github.com/normalize.css/).
+Download from the [project page](http://necolas.github.io/normalize.css/).
 
-Install with [Bower](http://twitter.github.com/bower/): `bower install --save normalize-css`
+Install with [Bower](http://twitter.github.io/bower/): `bower install --save normalize-css`
 
 ## What does it do?
 
@@ -42,7 +42,7 @@ override the defaults later in your CSS.
 ## Contribute
 
 Please read my [issue
-guidelines](https://github.com/necolas/issue-guidelines).
+guidelines](https://github.com/necolas/issue-guidelines/).
 
 ## Acknowledgements