Compatibility of refaster rules file not documented

### Description of the feature request:

Refaster writes serialized data into a file which then needs to be given to Error-Prone. As far as I could see it is nowhere documented whether this rule file is compatible between different versions. I.e., can I pass a rule file created with an older version to a newer error-prone, or vice versa?
If yes, for which version ranges is this guaranteed (e.g., same minor version, or just same major version)?

Please document the compatibility rules.

### What underlying problem are you trying to solve with this feature?

I am creating a set of refaster rules that would be useful for all of my organization's Java projects. I am trying to define a workflow of getting the rules to the users, and for this I would like to know whether I can pass around the binary rule file or whether the refaster rules should be distributed as source code and compiled just before they are applied.