Add MIT license

Provide a proper, highly permission license, recognized by the OSI, to
remove any potential for ambiguity. Addresses concerns around the
inability to elect to place work in the Public Domain.

Fix gh-1139
Separate normalize.css from main.css

Benefits of disentangling  normalize.css from the rest of the project's
CSS:

* Easier to track normalize.css version.
* Easier to update normalize.css.
* Easier to remove normalize.css if the user wants.
* Clearer distinction between normalizing CSS and the additions that
  HTML5 Boilerplate provides.

Drawback is the additional HTTP request incurred from the extra
stylesheet referenced in the HTML. However, we already do something
similar for the JS, and anyone serious about performance is going to
employ a build process to concatenate and minify CSS/JS.

Ref gh-1132
Ref gh-1140
Update jQuery 1.7.2 to jQuery 1.8.0

Ref gh-1161
Update CHANGELOG

Ref gh-1161
Docs: add info about using Metro tiles

Thanks to @Kroc for raising this issue and providing extra details. It
has been included in the 'extend' documentation alongside other IE tips.

Close gh-1136
Minor HTML indentation change
Simplify apple touch icons

Remove the radial gradient from around the star symbol.
Docs: minor tweaks
Update doc/extend.md

Added:
* IE10/Win8 badges
* Twitter Cards
* Chrome Web Store inline install
* iOS 6 Safari's Smart App Banners
Update to normalize.css v1.0.0
Docs: adjust line length and whitespace
htaccess: include a SymLinksIfOwnerMatch comment

Some web hosts disallows the use of the FollowSymLinks option in
.htaccess files, and suggest the use of SymLinksIfOwnerMatch.

Close gh-1147
Add "Hello world" to index.html

This avoids the default template rendering a completely blank page and
makes it easy for people to know straight away that things are
"working".

Fix gh-1165
Docs: update FAQ

Remove the section on "profiling" which was incomplete and not directly
linked to the code in this project. Also fix the headings so that
they're all of the same level.

Fix gh-1170
Add a HiDPI example media query

`-webkit-device-pixel-ratio` targets WebKit browsers.
`min-resolution` targets everything else.

Reference: http://www.w3.org/blog/CSS/2012/06/14/unprefix-webkit-device-pixel-ratio/

Fix gh-1127
Update to Normalize.css 1.0.1
Minor update to clearfix
Minor update to README
New image replacement approach

This approach uses a pseudo-element to force the element's content
downwards without covering the background of the element. The overflow
is hidden. For IE 6/7, fallback to the cruder `text-indent` method.

Known advantages:

* Works in IE6+ (although better in IE8+).

* Replaces any content in IE8+, including inner HTML.

* Nothing new for people to learn. Works just like all "traditional" IR
  techniques (unlike NIR, which needs you to add the image using a
  pseudo-element's `content` and relies margins for sprite positioning).

* Doesn't draw a large out-of-element box in modern browsers. You can
  even mix in something like `font: 10px/1 a` to reduce ce the size of
  the "off-screen" box, if you really need to.

* Doesn't have any potential SEO problems from `font-size:0`.

* Doesn't care about any minimum font-size that a browser might have.

* Doesn't have any potential failed-IR problems from inherited styles,
  like text being positioned within the element's visible box (i.e., if
  you use other properties like `text-stroke`).

Known issues:

* Doesn't work when images are off or fail to load (same as every other
  IR technique apart from NIR).

* If the IR'ed element has bottom-padding, then either it needs to be
  removed or the height of the pseudo-element needs to be bumped up
  (e.g., set to 200%).

* Doesn't avoid the `inline-block` bug in IE 6/7 due to the text-indent
  fallback for those browsers.

* Doesn't work on input elements (but they shouldn't be the subject of
  IR anyway).

* There is the potential for some final-result differences between
  IE 6/7 and modern browsers, but this is already the case with other IR
  techniques.

Fix gh-1149
Correct typo in the clearfix code