not support multi-process share-memory

[chinesejie]

I have test the code as follow.

1. Cacher.py
   set ht['b']='b'
   print ht['b']
   run "python -i Cacher.py"
   not close this process
2. Cacher2.py
   just print ht['b'] without setter
   run "python -i Cacher2.py"
   cannot get the value.

As I known, I think shared-memory could be read by two processes. How do you think about it.

[chinesejie]

sorry about that.

1. I forget to use ht.write_back() to update the item.
2. And the code "ht = MemCacher('test.Cacher', 1024, True)" will empty the mmap file. It should change to be "ht = MemCacher('test.Cacher', 1024, False)"
   Anyway, it is a really nice project.

[felix021]

这个扩展只是写着玩玩，我们的项目有多个python进程顺序跑，但是希望在进程之间共享一份数据，需求中暂时没有并发，而且真要写起来貌似也还是挺麻烦的，所以就偷懒了……目前并发读是没问题的，但是如果并发写的话估计是要崩的，慎用……