Make sync work for read instance

[Jochen Tackenberg]

Currently, the sync function writes changes to the DB/file/whatever. However, if I read from another instance pointing to the same dictionary, it will return the old value(s). It would be great if the sync function would also check if there were changes written to the dictionary (db/file) and read them (at best only the modified parts) to the cached dictionary.

I put a question on stackoverflow (see below), but from my current understanding there is simply no intended way!?

http://stackoverflow.com/questions/34592040/sync-function-of-shove-for-python3-useless-on-read?noredirect=1#comment56929569_34592040