Destroy unretained buffers when serializing project

Previously buffers could linger indefinitely if an error occurred
during startup between the deserialization of the project and the
original retaining edit session.

src/project.coffee

@@ -91,9 +91,14 @@ class Project
   serialize: ->
     state = @state.clone()
     state.set('path', @getPath())
+    @destroyUnretainedBuffers()
     state.set('buffers', buffer.serialize() for buffer in @getBuffers())
     state
 
+  # Private:
+  destroyUnretainedBuffers: ->
+     buffer.destroy() for buffer in @getBuffers() when not buffer.isRetained()
+
   # Public: ?
   getState: -> @state
 

src/text-buffer.coffee

@@ -81,13 +81,15 @@ class TextBuffer
       @destroyed = true
       @project?.removeBuffer(this)
 
+  isRetained: -> @refcount > 0
+
   retain: ->
     @refcount++
     this
 
   release: ->
     @refcount--
-    @destroy() if @refcount <= 0
+    @destroy() unless @isRetained()
     this
 
   serialize: ->