Don't explicitly reference global jQuery

Removes `window.jQuery` in favor of `jQuery`, fixes #10038
changed attr('data-target') to data('target');

this will extend js interface, to be possible to setup targets for tabs as 
    var content=$('<div class="tab-pane">',{text: 'content'});
    var tab=('<li>',{html: $('<a>',{text: 'Main options'})}).addClass('active').data({target: $main,toggle: 'tab'}).appendTo(tabs);
Add Welcome section to docs

* Fixes unrelated typo in readme
* Add new Welcome section with history, team, callouts, and community
subsections
* Redesigns callouts to be a bit lighterweight with colored headings
shorter avatar urls
use irc link
Merge branch 'master' into docs_welcome
adding required attribute for example signin form
Copy edits from @cvrebert and @juthilo
dat @juthilo edit
dat hash
move to separate about page
Dropdown in panel header does not inherit its colors

Fix for issue #10627
run grunt
Merge branch 'master' of github.com:twbs/bootstrap
include a copy of the CC-BY 3.0 License that the docs are under

downloaded from http://creativecommons.org/licenses/by/3.0/legalcode.txt
fixed issue where caret wouldn't inherit "active" li style on nav-pills, which caused the caret to stay blue
corrected caret colour when a nav dropdown is open
Show minification report for uglify-js.
Update jszip.js to the latest git.
Merge pull request #10710 from XhmikosR/patch-2

Patch 2