Add option to make squiggly-clojure use relative paths instead of absolute paths

I'm developing on a remote server using a port-forwarded nREPL connection. This use case doesn't work with squiggly-clojure because it sends absolute paths (which obviously don't exist on the server-side):

```
(-->
op "eval"
session "879ee11d-af76-43a6-9eee-ff7dddb860f4"
code "(do (require 'squiggly-clojure.core) (squiggly-clojure.core/check-kb 'stuff.things \"/Users/dkharlan/src/stuff/src/stuff/things.clj\"))"
id "74"
)

(...snip...)

(<--
id "74"
ns "user"
session "879ee11d-af76-43a6-9eee-ff7dddb860f4"
value "\"[{\\\"msg\\\":\\\"Kibit:\\\\/Users\\\\/dkharlan\\\\/src\\\\/stuff\\\\/src\\\\/stuff\\\\/things.clj (No such file or directory)\\\",\\\"column\\\":1,\\\"level\\\":\\\"error\\\",\\\"line\\\":1}]\""
)
```

Would it be possible to add a config option to allow using relative paths in this situation (and / or would you accept a PR for this)?