Revert "Project doesn't serialize non-modified buffers that don't exist on disk"

This reverts commit ec3e139632.

src/project.coffee

@@ -43,7 +43,6 @@ class Project extends telepath.Model
   # Private: Called by telepath.
   beforePersistence: ->
     @destroyUnretainedBuffers()
-    @destroyNonExistentNonModified()
 
   # Public: Register an opener for project files.
   #
@@ -78,9 +77,6 @@ class Project extends telepath.Model
   destroyUnretainedBuffers: ->
     buffer.destroy() for buffer in @getBuffers() when not buffer.isRetained()
 
-  destroyNonExistentNonModified: ->
-    buffer.destroy() for buffer in @getBuffers() when not buffer.isModified() and not buffer.file.exists()
-
   # Public: Returns the {Git} repository if available.
   getRepo: -> @repo