Show autocompletion as soon as "@" is typed

In order to show the autocompletion it was needed to type at least
another character after "@", so only the mentions that matched that
character were shown. Now the autocompletion is shown as soon as "@" is
typed, which shows all the possible mentions.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

apps/comments/js/commentstabview.js

@@ -185,9 +185,6 @@
 		},
 
 		_onAutoComplete: function(query, callback) {
-			if(_.isEmpty(query)) {
-				return;
-			}
 			var s = this;
 			if(!_.isUndefined(this._autoCompleteRequestTimer)) {
 				clearTimeout(this._autoCompleteRequestTimer);