Explicitly make pane active

Previously it relied on focus firing an event which will not occur
when not on the DOM.

spec/pane-container-spec.coffee

@@ -87,9 +87,6 @@ describe "PaneContainer", ->
       expect(panes).toEqual []
 
   describe ".reopenItem()", ->
-    beforeEach ->
-      pane3.makeActive()
-
     describe "when there is an active pane", ->
       it "reconstructs and shows the last-closed pane item", ->
         expect(container.getActivePane()).toBe pane3