update `this.context` with data context on query calls
Firefox Tab and Enter keys issue.

When item is selected by enter, the list is reopened.
Also pressing tab on focused element with drop list cause immediate reopening with empty search result list.
allow passing a function for maximumSelectionSize
Merge pull request #610 from MaxxSoftware/master

Firefox Tab and Enter keys issue.
ready for single
add third param to matcher in local
add default initselection for single and multi
Merge pull request #715 from vitalets/default-initselection-hidden

Default initSelection() for hidden element
Fix for jQuery 1.9
Merge pull request #727 from Schlogen/master

jQuery 1.9 Fixes
Update select2.js

missing parenthesis at line :1448 & :1845
Merge pull request #735 from vlycser/patch-1

Update select2.js
fix parenthesis mismatches
allow ajax.data to be undefined. fixes #732
Avoid error when label has no matching element

$('#no_such_element').data("select2") returns null rather than
undefined (jQuery 1.9.0).
Merge pull request #736 from tamias/label_no_element

Avoid error when label has no matching element
Use tags correctly when set as a function.
Merge pull request #738 from arnar/master

Wrap tags correctly when passed as a function.
Update select2.js

Fixed issues with select2 and disabled options, most of it having to do with incorrectly determining the index of an option when disabled options were being displayed.
Update select2.css

Made disabled results show up disabled, and added a class "selected" for elements that have already been selected (by default, these elements are hidden).