Snapshot support

It would be nice to have option '--db' which allows to load preconfigured blockchain snapshot.
Zipped snapshot as example can be found there https://s3.amazonaws.com/testrpc-shapshots/07d00cc515e0f9825b81595386b358593b7a3d6f.zip

Why this is important ? Developers can deploy a set of smart contracts once and then use it many times for testing some libraries.