Changed icon to match selectmenu widget

http://wiki.jqueryui.com/w/page/12138056/Selectmenu

Probably the markup of the button should changed too to match the button widget from jQuery UI Core - so it could fit nicely into existing projects.
Merge pull request #347 from doits/fixid

Fix id duplication
Update src/jquery.multiselect.filter.js

Fixed error menu is undefined error on line 32. Changed .data('multiselect'); to .data('echMultiselect');
Added var _self = this; on line 62 of the toggleChecked override function so that the options in the original select get modified when checks get toggled.
Merge pull request #386 from davidworkman9/patch-1

Update src/jquery.multiselect.filter.js
Make the filter widget 1.8/1.9+ compatible
Fix a missing  property. Fixes #382
Check to make sure the event target isn't the menu in the document click handler. fixes #355
Merge pull request #333 from suit/patch-2

Changed icon to match selectmenu widget
Merge pull request #252 from doits/fixIE

Fix IE JS Error if first item is disabled
jquery.multiselect.js - add 'appendMenuTo' option

Add the 'appendMenuTo' option, to enable appending the menu to some other 
parent element, other than the document's body.
This is very helpful when trying to apply specific CSS or behavior to the menu. 
Merge pull request #413 from mohoch1/master

 'appendMenuTo' option
fix appendTo option

document.body was not available before (at least in chrome 26).
additionally corrected wrong naming of option.
Merge branch 'master' into optgroups

Conflicts:
	src/jquery.multiselect.js
Merge remote-tracking branch 'remotes/doits/master' into doits-combined
Merge remote-tracking branch 'remotes/doits/fixAppendTo' into doits-combined
Merge remote-tracking branch 'remotes/doits/optgroups' into doits-combined