Add signal documentation for graphicsscene

pyqtgraph/GraphicsScene/GraphicsScene.py

@@ -37,6 +37,18 @@ class GraphicsScene(QtGui.QGraphicsScene):
     *  Eats mouseMove events that occur too soon after a mouse press.
     *  Reimplements items() and itemAt() to circumvent PyQt bug
 
+    ====================== ==================================================================
+    **Signals**
+    sigMouseClicked(event) Emitted when the mouse is clicked over the scene. Use ev.pos() to
+                           get the click position relative to the item that was clicked on,
+                           or ev.scenePos() to get the click position in scene coordinates.
+                           See :class:`pyqtgraph.GraphicsScene.MouseClickEvent`.                        
+    sigMouseMoved(pos)     Emitted when the mouse cursor moves over the scene. The position
+                           is given in scene coordinates.
+    sigMouseHover(items)   Emitted when the mouse is moved over the scene. Items is a list
+                           of items under the cursor.
+    ====================== ==================================================================
+    
     Mouse interaction is as follows:
     
     1) Every time the mouse moves, the scene delivers both the standard hoverEnter/Move/LeaveEvents