Storage compatibility analysis tool

[yondonfu]

The current delegate proxy upgrade pattern we use for some of our contracts requires that any new implementation logic contracts must have a storage layout that is compatible with the storage layout of the proxy contract. At the moment, this check is done manually by the developer. In order to develop stronger confidence in the safety of an upgrade, this check should instead be done automatically by an analysis tool.

The ZeppelinOS team is working on a solution for this. See: https://github.com/zeppelinos/zos/issues/37

We should track progress on the solution and incorporate it into this repo once it is ready for use.