Implement infinite scrolling

I't not perfect but it's a start.

js/glowingbear.js

@@ -539,6 +539,17 @@ weechat.controller('WeechatCtrl', ['$rootScope', '$scope', '$store', '$timeout',
         return connection.fetchMoreLines(numLines);
     };
 
+    $scope.infiniteScroll = function() {
+        // Check if we are already fetching
+        if ($rootScope.loadingLines) {
+            return;
+        }
+        var buffer = models.getActiveBuffer();
+        if (!buffer.allLinesFetched) {
+            $scope.fetchMoreLines();
+        }
+    };
+
     $rootScope.updateBufferBottom = function(bottom) {
             var eob = document.getElementById("end-of-buffer");
             var bl = document.getElementById('bufferlines');

js/whenscrolled-directive.js

@@ -0,0 +1,21 @@
+(function() {
+'use strict';
+
+var weechat = angular.module('weechat');
+weechat.directive('whenScrolled', function() {
+    return function(scope, elm, attr) {
+        var raw = elm[0];
+
+        var fun = function() {
+            if (raw.scrollTop === 0) {
+                scope.$apply(attr.whenScrolled);
+            }
+        };
+
+        elm.bind('scroll', function() {
+            _.debounce(fun, 200)();
+        });
+    };
+});
+
+})();