Refetch rendered markdown when triggering preview a subsequent time

src/packages/markdown-preview/lib/markdown-preview.coffee

@@ -17,6 +17,7 @@ module.exports =
     if nextPane = activePane.getNextPane()
       if preview = nextPane.itemForUri("markdown-preview:#{editSession.getPath()}")
         nextPane.showItem(preview)
+        preview.fetchRenderedMarkdown()
       else
         nextPane.showItem(new MarkdownPreviewView(editSession.buffer))
     else

src/packages/markdown-preview/spec/markdown-preview-spec.coffee

@@ -58,7 +58,9 @@ describe "MarkdownPreview package", ->
           expect(pane2.activeItem).not.toBe preview
           pane1.focus()
 
+          preview.fetchRenderedMarkdown.reset()
           rootView.getActiveView().trigger 'markdown-preview:show'
+          expect(preview.fetchRenderedMarkdown).toHaveBeenCalled()
           expect(rootView.getPanes()).toHaveLength 2
           expect(pane2.getItems()).toHaveLength 2
           expect(pane2.activeItem).toBe preview