Docs: Removed IRC channel links in CONTRIBUTING.md

GitHub doesn't support links with the irc protocol, so these were dead links.
Build: Upgrade to grunt-jquery-content 0.11.0
1.10.11
Sortable: Remove sender argument from 'remove' event description

Fixes #188
1.10.12
Sortable: Fix receive and remove descriptions

Make it clear that the events fire when the item is dropped and not just
dragged. Also, make it clear who receives the events.

Closes gh-190
1.10.13
Upgrade to jQuery UI 1.10.4
Update copyright year
1.10.14
jQuery.widget: Document that widget event names are lowercased

Fixes gh-182
Closes gh-191
jQuery.widget: Document the defaultElement property

Closes gh-192
jQuery.widget: _on() uses this.widget() for delegated events

Fixes gh-193
1.10.15
Button: Improve accessibility for checkbox/radio buttons

Fixes gh-185
Closes gh-195
1.10.16
Button: fix typo in link to icons option

Closes gh-196
jQuery.widget: added missing closing parentheses
jQuery.widget: Add link to learn articles

Closes gh-199
1.10.17