Docs: Add `Separate mobile URLs` subsection

Inform users that, if they use separate URLs for desktop and mobile
users, they should consider helping search engine algorithms better
understand the configuration on their web site.

See also:

 * https://developers.google.com/webmasters/smartphone-sites/details#separateurls
 * https://developers.google.com/webmasters/smartphone-sites/feature-phones

Close #1504.
Make consistency changes

Change code indentation in `normalize.css` from 2 to 4 spaces. This
is done in order to be consistent with the indentation used in the
other files.
Update to Apache Server Configs 2.2.0
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 (same as Safari for iOS does with the `apple-touch-icons` when
the user touches the `share` button).

Adding the `/browserconfig.xml` file 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

Close #1481.
Docs: Use Bootstrap instead of "Twitter Bootstrap"

"Twitter Bootstrap" is now simply known as "Bootstrap".

Ref: http://getbootstrap.com/about/#brand

Thanks @cvrebert.
Docs: Fix typo in `extend.md`

Close #1510.
Docs: Improve content about use of CDN for jQuery

Ref: https://github.com/h5bp/html5-boilerplate/issues/1498#issuecomment-33163993.
Close: #1511, #1514.
Update `CHANGELOG.md`

Include missing reference.
Docs: Update content regarding `Google Analytics`

Close: h5bp/html5-boilerplate#1490
       h5bp/html5-boilerplate#1515
Docs: Make minor grammar change in `extend.md`

Close h5bp/html5-boilerplate#1517.
Update to Normalize.css 3.0.1
Use `<!doctype html>` instead of `<!DOCTYPE html>`

Return back to the lowercase doctype in order to be more consistent
with the lowercase of the html tags.

References:

  * h5bp/html5-boilerplate#1522
  * http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#the-doctype

Close h5bp/html5-boilerplate#1522.
Update to Apache Server Configs v2.3.0
Make inline comments from main.css more consistent
Further optimize `tile` images

 * tile.png

     before:        13767 B
     after:         13743 B
     ──────────────────────
     reduction:        24 B [0.17%]

 * tile-wide.png

     before:         6781 B
     after:          6774 B
     ──────────────────────
     reduction:         7 B [0.10%]
Update to Modernizr v2.8.0
Add `newline` at the end of the gitattributes file

Under UNIX-like OSes, a text file consists of a series of lines, each
of which ends with a `newline` character (`\n`). A file that is not
empty and does not end with a `newline` is therefore considered not to
be a text file.

Because of this, utilities that are supposed to operate on text files
may not cope well with files that don't end with a `newline` (e.g.: they
might ignore the text after the last `newline`).

Adding the `newline` character at the end of the file ensures that users
won't encounter any odd behavior when using it.

Reference/Source: http://unix.stackexchange.com/a/18789.
Update print related comments in `main.css` file

Use correct terminology and remove the outdated parts of the comments.

See also:

 * JavaScript URIs:
   https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/void#JavaScript_URIs

 * URL fragments:
   http://www.whatwg.org/specs/web-apps/current-work/multipage/history.html#scroll-to-fragid

 * `href` attribute:
   http://www.whatwg.org/specs/web-apps/current-work/multipage/semantics.html#attr-link-href
   https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#attr-href
Fix file system permissions for `normalize.css`

Close #1537.
Remove empty line from `main.js`

Close h5bp/html5-boilerplate#1538.