fix(typeahead): don't close popup on right click

- Ensure typeahead popup does not dismiss on right click in Firefox

Closes #3975
Fixes #3973

Author: wesleycho

src/typeahead/typeahead.js

@@ -377,7 +377,9 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position', 'ui.bootstrap
 
       // Keep reference to click handler to unbind it.
       var dismissClickHandler = function (evt) {
-        if (element[0] !== evt.target) {
+        // Issue #3973
+        // Firefox treats right click as a click on document
+        if (element[0] !== evt.target && evt.which !== 3) {
           resetMatches();
           if (!$rootScope.$$phase) {
             scope.$digest();