Destroy items on pane:close

Previously pane:close would do nothing because of the guards in
Pane::destroy.

Also renames the menu to Close Pane to be more accurate.

Closes #1686

menus/darwin.cson

@@ -38,7 +38,7 @@
       { label: 'Save All', command: 'window:save-all' }
       { type: 'separator' }
       { label: 'Close Buffer', command: 'core:close' }
-      { label: 'Close All Buffers', command: 'pane:close' }
+      { label: 'Close Pane', command: 'pane:close' }
       { label: 'Close Window', command: 'window:close' }
     ]
   }

src/pane-view.coffee

@@ -75,7 +75,9 @@ class PaneView extends View
     @command 'pane:split-right', => @splitRight(@copyActiveItem())
     @command 'pane:split-up', => @splitUp(@copyActiveItem())
     @command 'pane:split-down', => @splitDown(@copyActiveItem())
-    @command 'pane:close', => @model.destroy()
+    @command 'pane:close', =>
+      @model.destroyItems()
+      @model.destroy()
     @command 'pane:close-other-items', => @destroyInactiveItems()
 
   # Deprecated: Use ::destroyItem