ivaynberg/select2 — pull request #2206 by MattSurabian (2014-03-24 16:37:40+00:00)
Title: Allow user to specify only drop down behavior

User adjustable option to force drop down behavior and prevent direction change.

Don't think an `allowDropdown` option is necessary, both because it seems non-intuitive, and one could use the existing `dropdownCssClass` option to add the class `select2-drop-above` to the dropdown div, thereby ensuring only dropup behavior.