`RefasterRuleCompiler` ignores all but one input file

First of all: Refaster is awesome. Defining new rules is child's play. Super cool!

While playing around with it I defined a number of rewrite rules. If possible I'd like pass all of these to Error Prone in one go. But, while cursory look at the `RefasterRuleCompiler` indicates that it outputs a _list_ of `CodeTransformer`s to the file specified using the `--out` flag, only one of the input `.java` files actually contributes to the output. Would it be possible to combine multiple before/after templates into a single `.refaster` file?

(I'm not familiar with `javac` internals, but if you give me some pointers I'm willing to implement this generalization. Provided that you think this is a sound idea in the first place, of course.)