Recompile LFE files when they change

[oubiwann]

Depends upon #106

Part of epic #102

[oubiwann]

Okay, got something in place for LFE files. Tried all sorts of approaches, including multiple incarnations of using the rebar3 plugins (via the rebar_agent) but that didn't go wall. Ended up opting for using lfe_comp directly.

One thing to keep in mind: If you are making changes to the watcher module, this won't work for more than 2 saves & reloads. This has to do with 1) the number of code revisions the VM will track, and 2) the ability (or lack thereof) to purge the watcher functions. It my be the I just need to relinquish all references to the watcher functions (since unwatching by itself didn't seem to be enough) ... so maybe shutting down inotify and starting it up again? Anyway, I think it's an edge case, so I'm not putting too much time into it.