Camomile's config files are incompatible with js_of_ocaml

[nmsmith]

Camomile's config file stuff relies on there being a file system that can be written to. This approach doesn't translate to the browser setting. A js_of_ocaml app that uses Camomile as a dependency experiences a runtime error "File does not exist" when it tries to load a config file upon starting.

This error seems to occur when the js_of_ocaml app is built in debug mode with separate compilation, but the config file access is somehow optimized away in release builds.