Store pathToOpen using new atom.set/getWindowState api

When you use `setWindowState`, your data is saved across refreshes.
You can only store state that can be serialized to JSON.

src/app/atom.coffee

@@ -109,3 +109,16 @@ _.extend atom,
     if name is 'reply'
       [messageId, callbackIndex] = data.shift()
       @pendingBrowserProcessCallbacks[messageId]?[callbackIndex]?(data...)
+
+  setWindowState: (keyPath, value) ->
+    windowState = @getWindowState()
+    _.setValueForKeyPath(windowState, keyPath, value)
+    $native.setWindowState(JSON.stringify(windowState))
+    windowState
+
+  getWindowState: (keyPath) ->
+    windowState = JSON.parse($native.getWindowState())
+    if keyPath
+      _.valueForKeyPath(windowState, keyPath)
+    else
+      windowState

src/app/window.coffee

@@ -47,8 +47,10 @@ windowAdditions =
       false
 
   shutdown: ->
-    @rootView?.deactivate()
-    @rootView = null
+    if @rootView
+      atom.setWindowState('pathToOpen', @rootView.project.getPath())
+      @rootView.deactivate()
+      @rootView = null
     $(window).unbind('focus')
     $(window).unbind('blur')
     $(window).off('before')

src/window-bootstrap.coffee

@@ -1,4 +1,6 @@
 # Like sands through the hourglass, so are the days of our lives.
 require 'atom'
 require 'window'
-window.attachRootView(window.location.params.pathToOpen)
+
+pathToOpen = atom.getWindowState('pathToOpen') ? window.location.params.pathToOpen
+window.attachRootView(pathToOpen)