Update screenshot links in README.

README.md

@@ -23,12 +23,12 @@ refreshes. All checking and record keeping is done on the server side.
 The following screenshot shows the Drag and Drop XBlock rendered
 inside the edX LMS before the user starts solving the problem:
 
-![Student view start](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/5ff71f56ba454c66d8f2749bc1d55d5f1df3b792/doc/img/student-view-start.png)
+![Student view start](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/c955a38dc3a1aaf609c586d293ce19b282e11ffd/doc/img/student-view-start.png)
 
 This screenshot shows the XBlock after the student successfully
 completed the Drag and Drop problem:
 
-![Student view finish](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/5ff71f56ba454c66d8f2749bc1d55d5f1df3b792/doc/img/student-view-finish.png)
+![Student view finish](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/c955a38dc3a1aaf609c586d293ce19b282e11ffd/doc/img/student-view-finish.png)
 
 Installation
 ------------
@@ -94,7 +94,7 @@ Usage
 The Drag and Drop XBlock features an interactive editor. Add the Drag
 and Drop component to a lesson, then click the `EDIT` button.
 
-![Edit view](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/5ff71f56ba454c66d8f2749bc1d55d5f1df3b792/doc/img/edit-view.png)
+![Edit view](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/c955a38dc3a1aaf609c586d293ce19b282e11ffd/doc/img/edit-view.png)
 
 In the first step, you can set some basic properties of the component,
 such as the title, the maximum score, the question text to render
@@ -102,7 +102,7 @@ above the background image, the introductory feedback (shown
 initially), and the final feedback (shown after the student
 successfully completes the drag and drop problem).
 
-![Drop zone edit](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/5ff71f56ba454c66d8f2749bc1d55d5f1df3b792/doc/img/edit-view-zones.png)
+![Drop zone edit](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/c955a38dc3a1aaf609c586d293ce19b282e11ffd/doc/img/edit-view-zones.png)
 
 In the next step, you set the URL and description for the background
 image and define the properties of the drop zones. For each zone you
@@ -114,7 +114,7 @@ whether or not to display borders outlining the zones. It is possible
 to define an arbitrary number of drop zones as long as their labels
 are unique.
 
-![Drag item edit](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/5ff71f56ba454c66d8f2749bc1d55d5f1df3b792/doc/img/edit-view-items.png)
+![Drag item edit](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/c955a38dc3a1aaf609c586d293ce19b282e11ffd/doc/img/edit-view-items.png)
 
 In the final step, you define the background and text color for drag
 items, as well as the drag items themselves. A drag item can contain
@@ -133,7 +133,7 @@ margin, the value entered by the student will be considered correct if
 it does not differ from the expected value by more than that margin
 (and incorrect otherwise).
 
-![Zone dropdown](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/5ff71f56ba454c66d8f2749bc1d55d5f1df3b792/doc/img/edit-view-zone-dropdown.png)
+![Zone dropdown](https://raw.githubusercontent.com/edx-solutions/xblock-drag-and-drop-v2/c955a38dc3a1aaf609c586d293ce19b282e11ffd/doc/img/edit-view-zone-dropdown.png)
 
 The zone that an item belongs to is selected from a dropdown that
 includes all drop zones defined in the previous step and a `none`